use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy}; use crate::ast::{GenericBound, TraitBoundModifier}; use crate::ast::Unsafety; use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind}; use crate::ast::Block; use crate::ast::{BlockCheckMode, CaptureBy, Movability}; use crate::ast::{Constness, Crate}; use crate::ast::Defaultness; use crate::ast::EnumDef; use crate::ast::{Expr, ExprKind, RangeLimits}; use crate::ast::{Field, FnDecl, FnHeader}; use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy}; use crate::ast::{GenericParam, GenericParamKind}; use crate::ast::GenericArg; use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind}; use crate::ast::{Label, Lifetime, Lit, LitKind}; use crate::ast::Local; use crate::ast::MacStmtStyle; use crate::ast::{Mac, Mac_, MacDelimiter}; use crate::ast::{MutTy, Mutability}; use crate::ast::{Pat, PatKind, PathSegment}; use crate::ast::{PolyTraitRef, QSelf}; use crate::ast::{Stmt, StmtKind}; use crate::ast::{VariantData, StructField}; use crate::ast::StrStyle; use crate::ast::SelfKind; use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax}; use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds}; use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar}; use crate::ast::{UseTree, UseTreeKind}; use crate::ast::{BinOpKind, UnOp}; use crate::ast::{RangeEnd, RangeSyntax}; use crate::{ast, attr}; use crate::ext::base::DummyResult; use crate::source_map::{self, SourceMap, Spanned, respan}; use crate::parse::{self, SeqSep, classify, token}; use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace}; use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration}; use crate::parse::token::DelimToken; use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership}; use crate::util::parser::{AssocOp, Fixity}; use crate::print::pprust; use crate::ptr::P; use crate::parse::PResult; use crate::ThinVec; use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint}; use crate::symbol::{Symbol, keywords}; use errors::{Applicability, DiagnosticBuilder, DiagnosticId}; use rustc_target::spec::abi::{self, Abi}; use syntax_pos::{Span, MultiSpan, BytePos, FileName}; use log::{debug, trace}; use std::borrow::Cow; use std::cmp; use std::mem; use std::path::{self, Path, PathBuf}; use std::slice; #[derive(Debug)] /// Whether the type alias or associated type is a concrete type or an existential type pub enum AliasKind { /// Just a new name for the same type Weak(P<Ty>), /// Only trait impls of the type will be usable, not the actual type itself Existential(GenericBounds), } bitflags::bitflags! { struct Restrictions: u8 { const STMT_EXPR = 1 << 0; const NO_STRUCT_LITERAL = 1 << 1; } } type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>); /// Specifies how to parse a path. #[derive(Copy, Clone, PartialEq)] pub enum PathStyle { /// In some contexts, notably in expressions, paths with generic arguments are ambiguous /// with something else. For example, in expressions `segment < ....` can be interpreted /// as a comparison and `segment ( ....` can be interpreted as a function call. /// In all such contexts the non-path interpretation is preferred by default for practical /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g. /// `x<y>` - comparisons, `x::<y>` - unambiguously a path. Expr, /// In other contexts, notably in types, no ambiguity exists and paths can be written /// without the disambiguator, e.g., `x<y>` - unambiguously a path. /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too. Type, /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports, /// visibilities or attributes. /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead /// (paths in "mod" contexts have to be checked later for absence of generic arguments /// anyway, due to macros), but it is used to avoid weird suggestions about expected /// tokens when something goes wrong. Mod, } #[derive(Clone, Copy, PartialEq, Debug)] enum SemiColonMode { Break, Ignore, Comma, } #[derive(Clone, Copy, PartialEq, Debug)] enum BlockMode { Break, Ignore, } /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression /// dropped into the token stream, which happens while parsing the result of /// macro expansion). Placement of these is not as complex as I feared it would /// be. The important thing is to make sure that lookahead doesn't balk at /// `token::Interpolated` tokens. macro_rules! maybe_whole_expr { ($p:expr) => { if let token::Interpolated(nt) = $p.token.clone() { match *nt { token::NtExpr(ref e) | token::NtLiteral(ref e) => { $p.bump(); return Ok((*e).clone()); } token::NtPath(ref path) => { $p.bump(); let span = $p.span; let kind = ExprKind::Path(None, (*path).clone()); return Ok($p.mk_expr(span, kind, ThinVec::new())); } token::NtBlock(ref block) => { $p.bump(); let span = $p.span; let kind = ExprKind::Block((*block).clone(), None); return Ok($p.mk_expr(span, kind, ThinVec::new())); } _ => {}, }; } } } /// As maybe_whole_expr, but for things other than expressions macro_rules! maybe_whole { ($p:expr, $constructor:ident, |$x:ident| $e:expr) => { if let token::Interpolated(nt) = $p.token.clone() { if let token::$constructor($x) = (*nt).clone() { $p.bump(); return Ok($e); } } }; } fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> { if let Some(ref mut rhs) = rhs { lhs.append(rhs); } lhs } #[derive(Debug, Clone, Copy, PartialEq)] enum PrevTokenKind { DocComment, Comma, Plus, Interpolated, Eof, Ident, Other, } trait RecoverQPath: Sized { const PATH_STYLE: PathStyle = PathStyle::Expr; fn to_ty(&self) -> Option<P<Ty>>; fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self; fn to_string(&self) -> String; } impl RecoverQPath for Ty { const PATH_STYLE: PathStyle = PathStyle::Type; fn to_ty(&self) -> Option<P<Ty>> { Some(P(self.clone())) } fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self { Self { span: path.span, node: TyKind::Path(qself, path), id: self.id } } fn to_string(&self) -> String { pprust::ty_to_string(self) } } impl RecoverQPath for Pat { fn to_ty(&self) -> Option<P<Ty>> { self.to_ty() } fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self { Self { span: path.span, node: PatKind::Path(qself, path), id: self.id } } fn to_string(&self) -> String { pprust::pat_to_string(self) } } impl RecoverQPath for Expr { fn to_ty(&self) -> Option<P<Ty>> { self.to_ty() } fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self { Self { span: path.span, node: ExprKind::Path(qself, path), id: self.id, attrs: self.attrs.clone() } } fn to_string(&self) -> String { pprust::expr_to_string(self) } } /* ident is handled by common.rs */ #[derive(Clone)] pub struct Parser<'a> { pub sess: &'a ParseSess, /// the current token: pub token: token::Token, /// the span of the current token: pub span: Span, /// the span of the previous token: meta_var_span: Option<Span>, pub prev_span: Span, /// the previous token kind prev_token_kind: PrevTokenKind, restrictions: Restrictions, /// Used to determine the path to externally loaded source files crate directory: Directory<'a>, /// Whether to parse sub-modules in other files. pub recurse_into_file_modules: bool, /// Name of the root module this parser originated from. If `None`, then the /// name is not known. This does not change while the parser is descending /// into modules, and sub-parsers have new values for this name. pub root_module_name: Option<String>, crate expected_tokens: Vec<TokenType>, token_cursor: TokenCursor, desugar_doc_comments: bool, /// Whether we should configure out of line modules as we parse. pub cfg_mods: bool, /// This field is used to keep track of how many left angle brackets we have seen. This is /// required in order to detect extra leading left angle brackets (`<` characters) and error /// appropriately. /// /// See the comments in the `parse_path_segment` function for more details. crate unmatched_angle_bracket_count: u32, crate max_angle_bracket_count: u32, /// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery /// it gets removed from here. Every entry left at the end gets emitted as an independent /// error. crate unclosed_delims: Vec<UnmatchedBrace>, } #[derive(Clone)] struct TokenCursor { frame: TokenCursorFrame, stack: Vec<TokenCursorFrame>, } #[derive(Clone)] struct TokenCursorFrame { delim: token::DelimToken, span: DelimSpan, open_delim: bool, tree_cursor: tokenstream::Cursor, close_delim: bool, last_token: LastToken, } /// This is used in `TokenCursorFrame` above to track tokens that are consumed /// by the parser, and then that's transitively used to record the tokens that /// each parse AST item is created with. /// /// Right now this has two states, either collecting tokens or not collecting /// tokens. If we're collecting tokens we just save everything off into a local /// `Vec`. This should eventually though likely save tokens from the original /// token stream and just use slicing of token streams to avoid creation of a /// whole new vector. /// /// The second state is where we're passively not recording tokens, but the last /// token is still tracked for when we want to start recording tokens. This /// "last token" means that when we start recording tokens we'll want to ensure /// that this, the first token, is included in the output. /// /// You can find some more example usage of this in the `collect_tokens` method /// on the parser. #[derive(Clone)] enum LastToken { Collecting(Vec<TreeAndJoint>), Was(Option<TreeAndJoint>), } impl TokenCursorFrame { fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self { TokenCursorFrame { delim: delim, span: sp, open_delim: delim == token::NoDelim, tree_cursor: tts.clone().into_trees(), close_delim: delim == token::NoDelim, last_token: LastToken::Was(None), } } } impl TokenCursor { fn next(&mut self) -> TokenAndSpan { loop { let tree = if !self.frame.open_delim { self.frame.open_delim = true; TokenTree::open_tt(self.frame.span.open, self.frame.delim) } else if let Some(tree) = self.frame.tree_cursor.next() { tree } else if !self.frame.close_delim { self.frame.close_delim = true; TokenTree::close_tt(self.frame.span.close, self.frame.delim) } else if let Some(frame) = self.stack.pop() { self.frame = frame; continue } else { return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP } }; match self.frame.last_token { LastToken::Collecting(ref mut v) => v.push(tree.clone().into()), LastToken::Was(ref mut t) => *t = Some(tree.clone().into()), } match tree { TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp }, TokenTree::Delimited(sp, delim, tts) => { let frame = TokenCursorFrame::new(sp, delim, &tts); self.stack.push(mem::replace(&mut self.frame, frame)); } } } } fn next_desugared(&mut self) -> TokenAndSpan { let (sp, name) = match self.next() { TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name), tok => return tok, }; let stripped = strip_doc_comment_decoration(&name.as_str()); // Searches for the occurrences of `"#*` and returns the minimum number of `#`s // required to wrap the text. let mut num_of_hashes = 0; let mut count = 0; for ch in stripped.chars() { count = match ch { '"' => 1, '#' if count > 0 => count + 1, _ => 0, }; num_of_hashes = cmp::max(num_of_hashes, count); } let delim_span = DelimSpan::from_single(sp); let body = TokenTree::Delimited( delim_span, token::Bracket, [TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"), false)), TokenTree::Token(sp, token::Eq), TokenTree::Token(sp, token::Literal( token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None)) ] .iter().cloned().collect::<TokenStream>().into(), ); self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new( delim_span, token::NoDelim, &if doc_comment_style(&name.as_str()) == AttrStyle::Inner { [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body] .iter().cloned().collect::<TokenStream>().into() } else { [TokenTree::Token(sp, token::Pound), body] .iter().cloned().collect::<TokenStream>().into() }, ))); self.next() } } #[derive(Clone, PartialEq)] crate enum TokenType { Token(token::Token), Keyword(keywords::Keyword), Operator, Lifetime, Ident, Path, Type, Const, } impl TokenType { fn to_string(&self) -> String { match *self { TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)), TokenType::Keyword(kw) => format!("`{}`", kw.name()), TokenType::Operator => "an operator".to_string(), TokenType::Lifetime => "lifetime".to_string(), TokenType::Ident => "identifier".to_string(), TokenType::Path => "path".to_string(), TokenType::Type => "type".to_string(), TokenType::Const => "const".to_string(), } } } /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`, /// `IDENT<<u8 as Trait>::AssocTy>`. /// /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes /// that `IDENT` is not the ident of a fn trait. fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool { t == &token::ModSep || t == &token::Lt || t == &token::BinOp(token::Shl) } /// Information about the path to a module. pub struct ModulePath { name: String, path_exists: bool, pub result: Result<ModulePathSuccess, Error>, } pub struct ModulePathSuccess { pub path: PathBuf, pub directory_ownership: DirectoryOwnership, warn: bool, } pub enum Error { FileNotFoundForModule { mod_name: String, default_path: String, secondary_path: String, dir_path: String, }, DuplicatePaths { mod_name: String, default_path: String, secondary_path: String, }, UselessDocComment, InclusiveRangeWithNoEnd, } impl Error { fn span_err<S: Into<MultiSpan>>(self, sp: S, handler: &errors::Handler) -> DiagnosticBuilder<'_> { match self { Error::FileNotFoundForModule { ref mod_name, ref default_path, ref secondary_path, ref dir_path } => { let mut err = struct_span_err!(handler, sp, E0583, "file not found for module `{}`", mod_name); err.help(&format!("name the file either {} or {} inside the directory \"{}\"", default_path, secondary_path, dir_path)); err } Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => { let mut err = struct_span_err!(handler, sp, E0584, "file for module `{}` found at both {} and {}", mod_name, default_path, secondary_path); err.help("delete or rename one of them to remove the ambiguity"); err } Error::UselessDocComment => { let mut err = struct_span_err!(handler, sp, E0585, "found a documentation comment that doesn't document anything"); err.help("doc comments must come before what they document, maybe a comment was \ intended with `//`?"); err } Error::InclusiveRangeWithNoEnd => { let mut err = struct_span_err!(handler, sp, E0586, "inclusive range with no end"); err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)"); err } } } } #[derive(Debug)] enum LhsExpr { NotYetParsed, AttributesParsed(ThinVec<Attribute>), AlreadyParsed(P<Expr>), } impl From<Option<ThinVec<Attribute>>> for LhsExpr { fn from(o: Option<ThinVec<Attribute>>) -> Self { if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed } } } impl From<P<Expr>> for LhsExpr { fn from(expr: P<Expr>) -> Self { LhsExpr::AlreadyParsed(expr) } } /// Creates a placeholder argument. fn dummy_arg(span: Span) -> Arg { let ident = Ident::new(keywords::Invalid.name(), span); let pat = P(Pat { id: ast::DUMMY_NODE_ID, node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None), span, }); let ty = Ty { node: TyKind::Err, span, id: ast::DUMMY_NODE_ID }; Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID } } #[derive(Copy, Clone, Debug)] enum TokenExpectType { Expect, NoExpect, } impl<'a> Parser<'a> { pub fn new(sess: &'a ParseSess, tokens: TokenStream, directory: Option<Directory<'a>>, recurse_into_file_modules: bool, desugar_doc_comments: bool) -> Self { let mut parser = Parser { sess, token: token::Whitespace, span: syntax_pos::DUMMY_SP, prev_span: syntax_pos::DUMMY_SP, meta_var_span: None, prev_token_kind: PrevTokenKind::Other, restrictions: Restrictions::empty(), recurse_into_file_modules, directory: Directory { path: Cow::from(PathBuf::new()), ownership: DirectoryOwnership::Owned { relative: None } }, root_module_name: None, expected_tokens: Vec::new(), token_cursor: TokenCursor { frame: TokenCursorFrame::new( DelimSpan::dummy(), token::NoDelim, &tokens.into(), ), stack: Vec::new(), }, desugar_doc_comments, cfg_mods: true, unmatched_angle_bracket_count: 0, max_angle_bracket_count: 0, unclosed_delims: Vec::new(), }; let tok = parser.next_tok(); parser.token = tok.tok; parser.span = tok.sp; if let Some(directory) = directory { parser.directory = directory; } else if !parser.span.is_dummy() { if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) { path.pop(); parser.directory.path = Cow::from(path); } } parser.process_potential_macro_variable(); parser } fn next_tok(&mut self) -> TokenAndSpan { let mut next = if self.desugar_doc_comments { self.token_cursor.next_desugared() } else { self.token_cursor.next() }; if next.sp.is_dummy() { // Tweak the location for better diagnostics, but keep syntactic context intact. next.sp = self.prev_span.with_ctxt(next.sp.ctxt()); } next } /// Converts the current token to a string using `self`'s reader. pub fn this_token_to_string(&self) -> String { pprust::token_to_string(&self.token) } fn token_descr(&self) -> Option<&'static str> { Some(match &self.token { t if t.is_special_ident() => "reserved identifier", t if t.is_used_keyword() => "keyword", t if t.is_unused_keyword() => "reserved keyword", token::DocComment(..) => "doc comment", _ => return None, }) } fn this_token_descr(&self) -> String { if let Some(prefix) = self.token_descr() { format!("{} `{}`", prefix, self.this_token_to_string()) } else { format!("`{}`", self.this_token_to_string()) } } fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> { let token_str = pprust::token_to_string(t); Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str))) } crate fn unexpected<T>(&mut self) -> PResult<'a, T> { match self.expect_one_of(&[], &[]) { Err(e) => Err(e), Ok(_) => unreachable!(), } } /// Expects and consumes the token `t`. Signals an error if the next token is not `t`. pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> { if self.expected_tokens.is_empty() { if self.token == *t { self.bump(); Ok(false) } else { let token_str = pprust::token_to_string(t); let this_token_str = self.this_token_descr(); let mut err = self.fatal(&format!("expected `{}`, found {}", token_str, this_token_str)); let sp = if self.token == token::Token::Eof { // EOF, don't want to point at the following char, but rather the last token self.prev_span } else { self.sess.source_map().next_point(self.prev_span) }; let label_exp = format!("expected `{}`", token_str); match self.recover_closing_delimiter(&[t.clone()], err) { Err(e) => err = e, Ok(recovered) => { return Ok(recovered); } } let cm = self.sess.source_map(); match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) { (Ok(ref a), Ok(ref b)) if a.line == b.line => { // When the spans are in the same line, it means that the only content // between them is whitespace, point only at the found token. err.span_label(self.span, label_exp); } _ => { err.span_label(sp, label_exp); err.span_label(self.span, "unexpected token"); } } Err(err) } } else { self.expect_one_of(slice::from_ref(t), &[]) } } fn recover_closing_delimiter( &mut self, tokens: &[token::Token], mut err: DiagnosticBuilder<'a>, ) -> PResult<'a, bool> { let mut pos = None; // we want to use the last closing delim that would apply for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() { if tokens.contains(&token::CloseDelim(unmatched.expected_delim)) && Some(self.span) > unmatched.unclosed_span { pos = Some(i); } } match pos { Some(pos) => { // Recover and assume that the detected unclosed delimiter was meant for // this location. Emit the diagnostic and act as if the delimiter was // present for the parser's sake. // Don't attempt to recover from this unclosed delimiter more than once. let unmatched = self.unclosed_delims.remove(pos); let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim)); // We want to suggest the inclusion of the closing delimiter where it makes // the most sense, which is immediately after the last token: // // {foo(bar {}} // - ^ // | | // | help: `)` may belong here (FIXME: #58270) // | // unclosed delimiter if let Some(sp) = unmatched.unclosed_span { err.span_label(sp, "unclosed delimiter"); } err.span_suggestion_short( self.sess.source_map().next_point(self.prev_span), &format!("{} may belong here", delim.to_string()), delim.to_string(), Applicability::MaybeIncorrect, ); err.emit(); self.expected_tokens.clear(); // reduce errors Ok(true) } _ => Err(err), } } /// Expect next token to be edible or inedible token. If edible, /// then consume it; if inedible, then return without consuming /// anything. Signal a fatal error if next token is unexpected. pub fn expect_one_of( &mut self, edible: &[token::Token], inedible: &[token::Token], ) -> PResult<'a, bool /* recovered */> { fn tokens_to_string(tokens: &[TokenType]) -> String { let mut i = tokens.iter(); // This might be a sign we need a connect method on Iterator. let b = i.next() .map_or(String::new(), |t| t.to_string()); i.enumerate().fold(b, |mut b, (i, a)| { if tokens.len() > 2 && i == tokens.len() - 2 { b.push_str(", or "); } else if tokens.len() == 2 && i == tokens.len() - 2 { b.push_str(" or "); } else { b.push_str(", "); } b.push_str(&a.to_string()); b }) } if edible.contains(&self.token) { self.bump(); Ok(false) } else if inedible.contains(&self.token) { // leave it in the input Ok(false) } else { let mut expected = edible.iter() .map(|x| TokenType::Token(x.clone())) .chain(inedible.iter().map(|x| TokenType::Token(x.clone()))) .chain(self.expected_tokens.iter().cloned()) .collect::<Vec<_>>(); expected.sort_by_cached_key(|x| x.to_string()); expected.dedup(); let expect = tokens_to_string(&expected[..]); let actual = self.this_token_to_string(); let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 { let short_expect = if expected.len() > 6 { format!("{} possible tokens", expected.len()) } else { expect.clone() }; (format!("expected one of {}, found `{}`", expect, actual), (self.sess.source_map().next_point(self.prev_span), format!("expected one of {} here", short_expect))) } else if expected.is_empty() { (format!("unexpected token: `{}`", actual), (self.prev_span, "unexpected token after this".to_string())) } else { (format!("expected {}, found `{}`", expect, actual), (self.sess.source_map().next_point(self.prev_span), format!("expected {} here", expect))) }; let mut err = self.fatal(&msg_exp); if self.token.is_ident_named("and") { err.span_suggestion_short( self.span, "use `&&` instead of `and` for the boolean operator", "&&".to_string(), Applicability::MaybeIncorrect, ); } if self.token.is_ident_named("or") { err.span_suggestion_short( self.span, "use `||` instead of `or` for the boolean operator", "||".to_string(), Applicability::MaybeIncorrect, ); } let sp = if self.token == token::Token::Eof { // This is EOF, don't want to point at the following char, but rather the last token self.prev_span } else { label_sp }; match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt { TokenType::Token(t) => Some(t.clone()), _ => None, }).collect::<Vec<_>>(), err) { Err(e) => err = e, Ok(recovered) => { return Ok(recovered); } } let cm = self.sess.source_map(); match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) { (Ok(ref a), Ok(ref b)) if a.line == b.line => { // When the spans are in the same line, it means that the only content between // them is whitespace, point at the found token in that case: // // X | () => { syntax error }; // | ^^^^^ expected one of 8 possible tokens here // // instead of having: // // X | () => { syntax error }; // | -^^^^^ unexpected token // | | // | expected one of 8 possible tokens here err.span_label(self.span, label_exp); } _ if self.prev_span == syntax_pos::DUMMY_SP => { // Account for macro context where the previous span might not be // available to avoid incorrect output (#54841). err.span_label(self.span, "unexpected token"); } _ => { err.span_label(sp, label_exp); err.span_label(self.span, "unexpected token"); } } Err(err) } } /// Returns the span of expr, if it was not interpolated or the span of the interpolated token. fn interpolated_or_expr_span(&self, expr: PResult<'a, P<Expr>>) -> PResult<'a, (Span, P<Expr>)> { expr.map(|e| { if self.prev_token_kind == PrevTokenKind::Interpolated { (self.prev_span, e) } else { (e.span, e) } }) } fn expected_ident_found(&self) -> DiagnosticBuilder<'a> { let mut err = self.struct_span_err(self.span, &format!("expected identifier, found {}", self.this_token_descr())); if let token::Ident(ident, false) = &self.token { if ident.is_reserved() && !ident.is_path_segment_keyword() && ident.name != keywords::Underscore.name() { err.span_suggestion( self.span, "you can escape reserved keywords to use them as identifiers", format!("r#{}", ident), Applicability::MaybeIncorrect, ); } } if let Some(token_descr) = self.token_descr() { err.span_label(self.span, format!("expected identifier, found {}", token_descr)); } else { err.span_label(self.span, "expected identifier"); if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) { err.span_suggestion( self.span, "remove this comma", String::new(), Applicability::MachineApplicable, ); } } err } pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> { self.parse_ident_common(true) } fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> { match self.token { token::Ident(ident, _) => { if self.token.is_reserved_ident() { let mut err = self.expected_ident_found(); if recover { err.emit(); } else { return Err(err); } } let span = self.span; self.bump(); Ok(Ident::new(ident.name, span)) } _ => { Err(if self.prev_token_kind == PrevTokenKind::DocComment { self.span_fatal_err(self.prev_span, Error::UselessDocComment) } else { self.expected_ident_found() }) } } } /// Checks if the next token is `tok`, and returns `true` if so. /// /// This method will automatically add `tok` to `expected_tokens` if `tok` is not /// encountered. crate fn check(&mut self, tok: &token::Token) -> bool { let is_present = self.token == *tok; if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); } is_present } /// Consumes a token 'tok' if it exists. Returns whether the given token was present. pub fn eat(&mut self, tok: &token::Token) -> bool { let is_present = self.check(tok); if is_present { self.bump() } is_present } fn check_keyword(&mut self, kw: keywords::Keyword) -> bool { self.expected_tokens.push(TokenType::Keyword(kw)); self.token.is_keyword(kw) } /// If the next token is the given keyword, eats it and returns /// `true`. Otherwise, returns `false`. pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool { if self.check_keyword(kw) { self.bump(); true } else { false } } fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool { if self.token.is_keyword(kw) { self.bump(); true } else { false } } /// If the given word is not a keyword, signals an error. /// If the next token is not the given word, signals an error. /// Otherwise, eats it. fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> { if !self.eat_keyword(kw) { self.unexpected() } else { Ok(()) } } fn check_ident(&mut self) -> bool { if self.token.is_ident() { true } else { self.expected_tokens.push(TokenType::Ident); false } } fn check_path(&mut self) -> bool { if self.token.is_path_start() { true } else { self.expected_tokens.push(TokenType::Path); false } } fn check_type(&mut self) -> bool { if self.token.can_begin_type() { true } else { self.expected_tokens.push(TokenType::Type); false } } fn check_const_arg(&mut self) -> bool { if self.token.can_begin_const_arg() { true } else { self.expected_tokens.push(TokenType::Const); false } } /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=` /// and continues. If a `+` is not seen, returns `false`. /// /// This is used when token-splitting `+=` into `+`. /// See issue #47856 for an example of when this may occur. fn eat_plus(&mut self) -> bool { self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus))); match self.token { token::BinOp(token::Plus) => { self.bump(); true } token::BinOpEq(token::Plus) => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); self.bump_with(token::Eq, span); true } _ => false, } } /// Checks to see if the next token is either `+` or `+=`. /// Otherwise returns `false`. fn check_plus(&mut self) -> bool { if self.token.is_like_plus() { true } else { self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus))); false } } /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single /// `&` and continues. If an `&` is not seen, signals an error. fn expect_and(&mut self) -> PResult<'a, ()> { self.expected_tokens.push(TokenType::Token(token::BinOp(token::And))); match self.token { token::BinOp(token::And) => { self.bump(); Ok(()) } token::AndAnd => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); Ok(self.bump_with(token::BinOp(token::And), span)) } _ => self.unexpected() } } /// Expects and consumes an `|`. If `||` is seen, replaces it with a single /// `|` and continues. If an `|` is not seen, signals an error. fn expect_or(&mut self) -> PResult<'a, ()> { self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or))); match self.token { token::BinOp(token::Or) => { self.bump(); Ok(()) } token::OrOr => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); Ok(self.bump_with(token::BinOp(token::Or), span)) } _ => self.unexpected() } } fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) { match suffix { None => {/* everything ok */} Some(suf) => { let text = suf.as_str(); if text.is_empty() { self.span_bug(sp, "found empty literal suffix in Some") } let msg = format!("{} with a suffix is invalid", kind); self.struct_span_err(sp, &msg) .span_label(sp, msg) .emit(); } } } /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single /// `<` and continue. If `<-` is seen, replaces it with a single `<` /// and continue. If a `<` is not seen, returns false. /// /// This is meant to be used when parsing generics on a path to get the /// starting token. fn eat_lt(&mut self) -> bool { self.expected_tokens.push(TokenType::Token(token::Lt)); let ate = match self.token { token::Lt => { self.bump(); true } token::BinOp(token::Shl) => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); self.bump_with(token::Lt, span); true } token::LArrow => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); self.bump_with(token::BinOp(token::Minus), span); true } _ => false, }; if ate { // See doc comment for `unmatched_angle_bracket_count`. self.unmatched_angle_bracket_count += 1; self.max_angle_bracket_count += 1; debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count); } ate } fn expect_lt(&mut self) -> PResult<'a, ()> { if !self.eat_lt() { self.unexpected() } else { Ok(()) } } /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it /// with a single `>` and continues. If a `>` is not seen, signals an error. fn expect_gt(&mut self) -> PResult<'a, ()> { self.expected_tokens.push(TokenType::Token(token::Gt)); let ate = match self.token { token::Gt => { self.bump(); Some(()) } token::BinOp(token::Shr) => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); Some(self.bump_with(token::Gt, span)) } token::BinOpEq(token::Shr) => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); Some(self.bump_with(token::Ge, span)) } token::Ge => { let span = self.span.with_lo(self.span.lo() + BytePos(1)); Some(self.bump_with(token::Eq, span)) } _ => None, }; match ate { Some(_) => { // See doc comment for `unmatched_angle_bracket_count`. if self.unmatched_angle_bracket_count > 0 { self.unmatched_angle_bracket_count -= 1; debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count); } Ok(()) }, None => self.unexpected(), } } /// Eats and discards tokens until one of `kets` is encountered. Respects token trees, /// passes through any errors encountered. Used for error recovery. fn eat_to_tokens(&mut self, kets: &[&token::Token]) { let handler = self.diagnostic(); if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| Ok(p.parse_token_tree())) { handler.cancel(err); } } /// Parses a sequence, including the closing delimiter. The function /// `f` must consume tokens until reaching the next separator or /// closing bracket. pub fn parse_seq_to_end<T, F>(&mut self, ket: &token::Token, sep: SeqSep, f: F) -> PResult<'a, Vec<T>> where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>, { let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?; if !recovered { self.bump(); } Ok(val) } /// Parses a sequence, not including the closing delimiter. The function /// `f` must consume tokens until reaching the next separator or /// closing bracket. pub fn parse_seq_to_before_end<T, F>( &mut self, ket: &token::Token, sep: SeqSep, f: F, ) -> PResult<'a, (Vec<T>, bool)> where F: FnMut(&mut Parser<'a>) -> PResult<'a, T> { self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f) } fn parse_seq_to_before_tokens<T, F>( &mut self, kets: &[&token::Token], sep: SeqSep, expect: TokenExpectType, mut f: F, ) -> PResult<'a, (Vec<T>, bool /* recovered */)> where F: FnMut(&mut Parser<'a>) -> PResult<'a, T> { let mut first = true; let mut recovered = false; let mut v = vec![]; while !kets.iter().any(|k| { match expect { TokenExpectType::Expect => self.check(k), TokenExpectType::NoExpect => self.token == **k, } }) { match self.token { token::CloseDelim(..) | token::Eof => break, _ => {} }; if let Some(ref t) = sep.sep { if first { first = false; } else { match self.expect(t) { Ok(false) => {} Ok(true) => { recovered = true; break; } Err(mut e) => { // Attempt to keep parsing if it was a similar separator if let Some(ref tokens) = t.similar_tokens() { if tokens.contains(&self.token) { self.bump(); } } e.emit(); // Attempt to keep parsing if it was an omitted separator match f(self) { Ok(t) => { v.push(t); continue; }, Err(mut e) => { e.cancel(); break; } } } } } } if sep.trailing_sep_allowed && kets.iter().any(|k| { match expect { TokenExpectType::Expect => self.check(k), TokenExpectType::NoExpect => self.token == **k, } }) { break; } let t = f(self)?; v.push(t); } Ok((v, recovered)) } /// Parses a sequence, including the closing delimiter. The function /// `f` must consume tokens until reaching the next separator or /// closing bracket. fn parse_unspanned_seq<T, F>( &mut self, bra: &token::Token, ket: &token::Token, sep: SeqSep, f: F, ) -> PResult<'a, Vec<T>> where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>, { self.expect(bra)?; let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?; if !recovered { self.eat(ket); } Ok(result) } /// Advance the parser by one token pub fn bump(&mut self) { if self.prev_token_kind == PrevTokenKind::Eof { // Bumping after EOF is a bad sign, usually an infinite loop. self.bug("attempted to bump the parser past EOF (may be stuck in a loop)"); } self.prev_span = self.meta_var_span.take().unwrap_or(self.span); // Record last token kind for possible error recovery. self.prev_token_kind = match self.token { token::DocComment(..) => PrevTokenKind::DocComment, token::Comma => PrevTokenKind::Comma, token::BinOp(token::Plus) => PrevTokenKind::Plus, token::Interpolated(..) => PrevTokenKind::Interpolated, token::Eof => PrevTokenKind::Eof, token::Ident(..) => PrevTokenKind::Ident, _ => PrevTokenKind::Other, }; let next = self.next_tok(); self.span = next.sp; self.token = next.tok; self.expected_tokens.clear(); // check after each token self.process_potential_macro_variable(); } /// Advance the parser using provided token as a next one. Use this when /// consuming a part of a token. For example a single `<` from `<<`. fn bump_with(&mut self, next: token::Token, span: Span) { self.prev_span = self.span.with_hi(span.lo()); // It would be incorrect to record the kind of the current token, but // fortunately for tokens currently using `bump_with`, the // prev_token_kind will be of no use anyway. self.prev_token_kind = PrevTokenKind::Other; self.span = span; self.token = next; self.expected_tokens.clear(); } pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where F: FnOnce(&token::Token) -> R, { if dist == 0 { return f(&self.token) } f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) { Some(tree) => match tree { TokenTree::Token(_, tok) => tok, TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim), }, None => token::CloseDelim(self.token_cursor.frame.delim), }) } fn look_ahead_span(&self, dist: usize) -> Span { if dist == 0 { return self.span } match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) { Some(TokenTree::Token(span, _)) => span, Some(TokenTree::Delimited(span, ..)) => span.entire(), None => self.look_ahead_span(dist - 1), } } pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> { self.sess.span_diagnostic.struct_span_fatal(self.span, m) } pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> { self.sess.span_diagnostic.struct_span_fatal(sp, m) } fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> { err.span_err(sp, self.diagnostic()) } fn bug(&self, m: &str) -> ! { self.sess.span_diagnostic.span_bug(self.span, m) } fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) { self.sess.span_diagnostic.span_err(sp, m) } fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> { self.sess.span_diagnostic.struct_span_err(sp, m) } crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! { self.sess.span_diagnostic.span_bug(sp, m) } fn cancel(&self, err: &mut DiagnosticBuilder<'_>) { self.sess.span_diagnostic.cancel(err) } crate fn diagnostic(&self) -> &'a errors::Handler { &self.sess.span_diagnostic } /// Is the current token one of the keywords that signals a bare function type? fn token_is_bare_fn_keyword(&mut self) -> bool { self.check_keyword(keywords::Fn) || self.check_keyword(keywords::Unsafe) || self.check_keyword(keywords::Extern) } /// Parses a `TyKind::BareFn` type. fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> { /* [unsafe] [extern "ABI"] fn (S) -> T ^~~~^ ^~~~^ ^~^ ^ | | | | | | | Return type | | Argument types | | | ABI Function Style */ let unsafety = self.parse_unsafety(); let abi = if self.eat_keyword(keywords::Extern) { self.parse_opt_abi()?.unwrap_or(Abi::C) } else { Abi::Rust }; self.expect_keyword(keywords::Fn)?; let (inputs, variadic) = self.parse_fn_args(false, true)?; let ret_ty = self.parse_ret_ty(false)?; let decl = P(FnDecl { inputs, output: ret_ty, variadic, }); Ok(TyKind::BareFn(P(BareFnTy { abi, unsafety, generic_params, decl, }))) } /// Parses asyncness: `async` or nothing. fn parse_asyncness(&mut self) -> IsAsync { if self.eat_keyword(keywords::Async) { IsAsync::Async { closure_id: ast::DUMMY_NODE_ID, return_impl_trait_id: ast::DUMMY_NODE_ID, } } else { IsAsync::NotAsync } } /// Parses unsafety: `unsafe` or nothing. fn parse_unsafety(&mut self) -> Unsafety { if self.eat_keyword(keywords::Unsafe) { Unsafety::Unsafe } else { Unsafety::Normal } } /// Parses the items in a trait declaration. pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> { maybe_whole!(self, NtTraitItem, |x| x); let attrs = self.parse_outer_attributes()?; let (mut item, tokens) = self.collect_tokens(|this| { this.parse_trait_item_(at_end, attrs) })?; // See `parse_item` for why this clause is here. if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) { item.tokens = Some(tokens); } Ok(item) } fn parse_trait_item_(&mut self, at_end: &mut bool, mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> { let lo = self.span; let (name, node, generics) = if self.eat_keyword(keywords::Type) { self.parse_trait_item_assoc_ty()? } else if self.is_const_item() { self.expect_keyword(keywords::Const)?; let ident = self.parse_ident()?; self.expect(&token::Colon)?; let ty = self.parse_ty()?; let default = if self.eat(&token::Eq) { let expr = self.parse_expr()?; self.expect(&token::Semi)?; Some(expr) } else { self.expect(&token::Semi)?; None }; (ident, TraitItemKind::Const(ty, default), ast::Generics::default()) } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? { // trait item macro. (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default()) } else { let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?; let ident = self.parse_ident()?; let mut generics = self.parse_generics()?; let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| { // This is somewhat dubious; We don't want to allow // argument names to be left off if there is a // definition... // We don't allow argument names to be left off in edition 2018. p.parse_arg_general(p.span.rust_2018(), true) })?; generics.where_clause = self.parse_where_clause()?; let sig = ast::MethodSig { header: FnHeader { unsafety, constness, abi, asyncness, }, decl: d, }; let body = match self.token { token::Semi => { self.bump(); *at_end = true; debug!("parse_trait_methods(): parsing required method"); None } token::OpenDelim(token::Brace) => { debug!("parse_trait_methods(): parsing provided method"); *at_end = true; let (inner_attrs, body) = self.parse_inner_attrs_and_block()?; attrs.extend(inner_attrs.iter().cloned()); Some(body) } token::Interpolated(ref nt) => { match **nt { token::NtBlock(..) => { *at_end = true; let (inner_attrs, body) = self.parse_inner_attrs_and_block()?; attrs.extend(inner_attrs.iter().cloned()); Some(body) } _ => { let token_str = self.this_token_descr(); let mut err = self.fatal(&format!("expected `;` or `{{`, found {}", token_str)); err.span_label(self.span, "expected `;` or `{`"); return Err(err); } } } _ => { let token_str = self.this_token_descr(); let mut err = self.fatal(&format!("expected `;` or `{{`, found {}", token_str)); err.span_label(self.span, "expected `;` or `{`"); return Err(err); } }; (ident, ast::TraitItemKind::Method(sig, body), generics) }; Ok(TraitItem { id: ast::DUMMY_NODE_ID, ident: name, attrs, generics, node, span: lo.to(self.prev_span), tokens: None, }) } /// Parses an optional return type `[ -> TY ]` in a function declaration. fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> { if self.eat(&token::RArrow) { Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true)?)) } else { Ok(FunctionRetTy::Default(self.span.shrink_to_lo())) } } /// Parses a type. pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> { self.parse_ty_common(true, true) } /// Parses a type in restricted contexts where `+` is not permitted. /// /// Example 1: `&'a TYPE` /// `+` is prohibited to maintain operator priority (P(+) < P(&)). /// Example 2: `value1 as TYPE + value2` /// `+` is prohibited to avoid interactions with expression grammar. fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> { self.parse_ty_common(false, true) } fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool) -> PResult<'a, P<Ty>> { maybe_whole!(self, NtTy, |x| x); let lo = self.span; let mut impl_dyn_multi = false; let node = if self.eat(&token::OpenDelim(token::Paren)) { // `(TYPE)` is a parenthesized type. // `(TYPE,)` is a tuple with a single field of type TYPE. let mut ts = vec![]; let mut last_comma = false; while self.token != token::CloseDelim(token::Paren) { ts.push(self.parse_ty()?); if self.eat(&token::Comma) { last_comma = true; } else { last_comma = false; break; } } let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus; self.expect(&token::CloseDelim(token::Paren))?; if ts.len() == 1 && !last_comma { let ty = ts.into_iter().nth(0).unwrap().into_inner(); let maybe_bounds = allow_plus && self.token.is_like_plus(); match ty.node { // `(TY_BOUND_NOPAREN) + BOUND + ...`. TyKind::Path(None, ref path) if maybe_bounds => { self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)? } TyKind::TraitObject(ref bounds, TraitObjectSyntax::None) if maybe_bounds && bounds.len() == 1 && !trailing_plus => { let path = match bounds[0] { GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(), GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"), }; self.parse_remaining_bounds(Vec::new(), path, lo, true)? } // `(TYPE)` _ => TyKind::Paren(P(ty)) } } else { TyKind::Tup(ts) } } else if self.eat(&token::Not) { // Never type `!` TyKind::Never } else if self.eat(&token::BinOp(token::Star)) { // Raw pointer TyKind::Ptr(self.parse_ptr()?) } else if self.eat(&token::OpenDelim(token::Bracket)) { // Array or slice let t = self.parse_ty()?; // Parse optional `; EXPR` in `[TYPE; EXPR]` let t = match self.maybe_parse_fixed_length_of_vec()? { None => TyKind::Slice(t), Some(length) => TyKind::Array(t, AnonConst { id: ast::DUMMY_NODE_ID, value: length, }), }; self.expect(&token::CloseDelim(token::Bracket))?; t } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) { // Reference self.expect_and()?; self.parse_borrowed_pointee()? } else if self.eat_keyword_noexpect(keywords::Typeof) { // `typeof(EXPR)` // In order to not be ambiguous, the type must be surrounded by parens. self.expect(&token::OpenDelim(token::Paren))?; let e = AnonConst { id: ast::DUMMY_NODE_ID, value: self.parse_expr()?, }; self.expect(&token::CloseDelim(token::Paren))?; TyKind::Typeof(e) } else if self.eat_keyword(keywords::Underscore) { // A type to be inferred `_` TyKind::Infer } else if self.token_is_bare_fn_keyword() { // Function pointer type self.parse_ty_bare_fn(Vec::new())? } else if self.check_keyword(keywords::For) { // Function pointer type or bound list (trait object type) starting with a poly-trait. // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T` // `for<'lt> Trait1<'lt> + Trait2 + 'a` let lo = self.span; let lifetime_defs = self.parse_late_bound_lifetime_defs()?; if self.token_is_bare_fn_keyword() { self.parse_ty_bare_fn(lifetime_defs)? } else { let path = self.parse_path(PathStyle::Type)?; let parse_plus = allow_plus && self.check_plus(); self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)? } } else if self.eat_keyword(keywords::Impl) { // Always parse bounds greedily for better error recovery. let bounds = self.parse_generic_bounds(None)?; impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus; TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds) } else if self.check_keyword(keywords::Dyn) && (self.span.rust_2018() || self.look_ahead(1, |t| t.can_begin_bound() && !can_continue_type_after_non_fn_ident(t))) { self.bump(); // `dyn` // Always parse bounds greedily for better error recovery. let bounds = self.parse_generic_bounds(None)?; impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus; TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn) } else if self.check(&token::Question) || self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) { // Bound list (trait object type) TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?, TraitObjectSyntax::None) } else if self.eat_lt() { // Qualified path let (qself, path) = self.parse_qpath(PathStyle::Type)?; TyKind::Path(Some(qself), path) } else if self.token.is_path_start() { // Simple path let path = self.parse_path(PathStyle::Type)?; if self.eat(&token::Not) { // Macro invocation in type position let (delim, tts) = self.expect_delimited_token_tree()?; let node = Mac_ { path, tts, delim }; TyKind::Mac(respan(lo.to(self.prev_span), node)) } else { // Just a type path or bound list (trait object type) starting with a trait. // `Type` // `Trait1 + Trait2 + 'a` if allow_plus && self.check_plus() { self.parse_remaining_bounds(Vec::new(), path, lo, true)? } else { TyKind::Path(None, path) } } } else { let msg = format!("expected type, found {}", self.this_token_descr()); return Err(self.fatal(&msg)); }; let span = lo.to(self.prev_span); let ty = Ty { node, span, id: ast::DUMMY_NODE_ID }; // Try to recover from use of `+` with incorrect priority. self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty); self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?; let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?; Ok(P(ty)) } fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path, lo: Span, parse_plus: bool) -> PResult<'a, TyKind> { let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span)); let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)]; if parse_plus { self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded bounds.append(&mut self.parse_generic_bounds(None)?); } Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None)) } fn maybe_report_ambiguous_plus(&mut self, allow_plus: bool, impl_dyn_multi: bool, ty: &Ty) { if !allow_plus && impl_dyn_multi { let sum_with_parens = format!("({})", pprust::ty_to_string(&ty)); self.struct_span_err(ty.span, "ambiguous `+` in a type") .span_suggestion( ty.span, "use parentheses to disambiguate", sum_with_parens, Applicability::MachineApplicable ).emit(); } } fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> { // Do not add `+` to expected tokens. if !allow_plus || !self.token.is_like_plus() { return Ok(()) } self.bump(); // `+` let bounds = self.parse_generic_bounds(None)?; let sum_span = ty.span.to(self.prev_span); let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178, "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty)); match ty.node { TyKind::Rptr(ref lifetime, ref mut_ty) => { let sum_with_parens = pprust::to_string(|s| { use crate::print::pprust::PrintState; s.s.word("&")?; s.print_opt_lifetime(lifetime)?; s.print_mutability(mut_ty.mutbl)?; s.popen()?; s.print_type(&mut_ty.ty)?; s.print_type_bounds(" +", &bounds)?; s.pclose() }); err.span_suggestion( sum_span, "try adding parentheses", sum_with_parens, Applicability::MachineApplicable ); } TyKind::Ptr(..) | TyKind::BareFn(..) => { err.span_label(sum_span, "perhaps you forgot parentheses?"); } _ => { err.span_label(sum_span, "expected a path"); }, } err.emit(); Ok(()) } // Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`. fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: T, allow_recovery: bool) -> PResult<'a, T> { // Do not add `::` to expected tokens. if !allow_recovery || self.token != token::ModSep { return Ok(base); } let ty = match base.to_ty() { Some(ty) => ty, None => return Ok(base), }; self.bump(); // `::` let mut segments = Vec::new(); self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?; let span = ty.span.to(self.prev_span); let path_span = span.to(span); // use an empty path since `position` == 0 let recovered = base.to_recovered( Some(QSelf { ty, path_span, position: 0 }), ast::Path { segments, span }, ); self.diagnostic() .struct_span_err(span, "missing angle brackets in associated item path") .span_suggestion( // this is a best-effort recovery span, "try", recovered.to_string(), Applicability::MaybeIncorrect ).emit(); Ok(recovered) } fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> { let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None }; let mutbl = self.parse_mutability(); let ty = self.parse_ty_no_plus()?; return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl })); } fn parse_ptr(&mut self) -> PResult<'a, MutTy> { let mutbl = if self.eat_keyword(keywords::Mut) { Mutability::Mutable } else if self.eat_keyword(keywords::Const) { Mutability::Immutable } else { let span = self.prev_span; let msg = "expected mut or const in raw pointer type"; self.struct_span_err(span, msg) .span_label(span, msg) .help("use `*mut T` or `*const T` as appropriate") .emit(); Mutability::Immutable }; let t = self.parse_ty_no_plus()?; Ok(MutTy { ty: t, mutbl: mutbl }) } fn is_named_argument(&mut self) -> bool { let offset = match self.token { token::Interpolated(ref nt) => match **nt { token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon), _ => 0, } token::BinOp(token::And) | token::AndAnd => 1, _ if self.token.is_keyword(keywords::Mut) => 1, _ => 0, }; self.look_ahead(offset, |t| t.is_ident()) && self.look_ahead(offset + 1, |t| t == &token::Colon) } /// Skips unexpected attributes and doc comments in this position and emits an appropriate /// error. fn eat_incorrect_doc_comment(&mut self, applied_to: &str) { if let token::DocComment(_) = self.token { let mut err = self.diagnostic().struct_span_err( self.span, &format!("documentation comments cannot be applied to {}", applied_to), ); err.span_label(self.span, "doc comments are not allowed here"); err.emit(); self.bump(); } else if self.token == token::Pound && self.look_ahead(1, |t| { *t == token::OpenDelim(token::Bracket) }) { let lo = self.span; // Skip every token until next possible arg. while self.token != token::CloseDelim(token::Bracket) { self.bump(); } let sp = lo.to(self.span); self.bump(); let mut err = self.diagnostic().struct_span_err( sp, &format!("attributes cannot be applied to {}", applied_to), ); err.span_label(sp, "attributes are not allowed here"); err.emit(); } } /// This version of parse arg doesn't necessarily require identifier names. fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool) -> PResult<'a, Arg> { maybe_whole!(self, NtArg, |x| x); if let Ok(Some(_)) = self.parse_self_arg() { let mut err = self.struct_span_err(self.prev_span, "unexpected `self` argument in function"); err.span_label(self.prev_span, "`self` is only valid as the first argument of an associated function"); return Err(err); } let (pat, ty) = if require_name || self.is_named_argument() { debug!("parse_arg_general parse_pat (require_name:{})", require_name); self.eat_incorrect_doc_comment("method arguments"); let pat = self.parse_pat(Some("argument name"))?; if let Err(mut err) = self.expect(&token::Colon) { // If we find a pattern followed by an identifier, it could be an (incorrect) // C-style parameter declaration. if self.check_ident() && self.look_ahead(1, |t| { *t == token::Comma || *t == token::CloseDelim(token::Paren) }) { let ident = self.parse_ident().unwrap(); let span = pat.span.with_hi(ident.span.hi()); err.span_suggestion( span, "declare the type after the parameter binding", "<identifier>: <type>", Applicability::HasPlaceholders, ); } else if require_name && is_trait_item { if let PatKind::Ident(_, ident, _) = pat.node { err.span_suggestion( pat.span, "explicitly ignore parameter", format!("_: {}", ident), Applicability::MachineApplicable, ); } err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)"); } return Err(err); } self.eat_incorrect_doc_comment("a method argument's type"); (pat, self.parse_ty()?) } else { debug!("parse_arg_general ident_to_pat"); let parser_snapshot_before_ty = self.clone(); self.eat_incorrect_doc_comment("a method argument's type"); let mut ty = self.parse_ty(); if ty.is_ok() && self.token != token::Comma && self.token != token::CloseDelim(token::Paren) { // This wasn't actually a type, but a pattern looking like a type, // so we are going to rollback and re-parse for recovery. ty = self.unexpected(); } match ty { Ok(ty) => { let ident = Ident::new(keywords::Invalid.name(), self.prev_span); let pat = P(Pat { id: ast::DUMMY_NODE_ID, node: PatKind::Ident( BindingMode::ByValue(Mutability::Immutable), ident, None), span: ty.span, }); (pat, ty) } Err(mut err) => { // Recover from attempting to parse the argument as a type without pattern. err.cancel(); mem::replace(self, parser_snapshot_before_ty); let pat = self.parse_pat(Some("argument name"))?; self.expect(&token::Colon)?; let ty = self.parse_ty()?; let mut err = self.diagnostic().struct_span_err_with_code( pat.span, "patterns aren't allowed in methods without bodies", DiagnosticId::Error("E0642".into()), ); err.span_suggestion_short( pat.span, "give this argument a name or use an underscore to ignore it", "_".to_owned(), Applicability::MachineApplicable, ); err.emit(); // Pretend the pattern is `_`, to avoid duplicate errors from AST validation. let pat = P(Pat { node: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID }); (pat, ty) } } }; Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID }) } /// Parses a single function argument. crate fn parse_arg(&mut self) -> PResult<'a, Arg> { self.parse_arg_general(true, false) } /// Parses an argument in a lambda header (e.g., `|arg, arg|`). fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> { let pat = self.parse_pat(Some("argument name"))?; let t = if self.eat(&token::Colon) { self.parse_ty()? } else { P(Ty { id: ast::DUMMY_NODE_ID, node: TyKind::Infer, span: self.prev_span, }) }; Ok(Arg { ty: t, pat, id: ast::DUMMY_NODE_ID }) } fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> { if self.eat(&token::Semi) { Ok(Some(self.parse_expr()?)) } else { Ok(None) } } /// Matches `token_lit = LIT_INTEGER | ...`. fn parse_lit_token(&mut self) -> PResult<'a, LitKind> { let out = match self.token { token::Interpolated(ref nt) => match **nt { token::NtExpr(ref v) | token::NtLiteral(ref v) => match v.node { ExprKind::Lit(ref lit) => { lit.node.clone() } _ => { return self.unexpected_last(&self.token); } }, _ => { return self.unexpected_last(&self.token); } }, token::Literal(lit, suf) => { let diag = Some((self.span, &self.sess.span_diagnostic)); let (suffix_illegal, result) = parse::lit_token(lit, suf, diag); if suffix_illegal { let sp = self.span; self.expect_no_suffix(sp, lit.literal_name(), suf) } result.unwrap() } token::Dot if self.look_ahead(1, |t| match t { token::Literal(parse::token::Lit::Integer(_) , _) => true, _ => false, }) => { // recover from `let x = .4;` let lo = self.span; self.bump(); if let token::Literal( parse::token::Lit::Integer(val), suffix, ) = self.token { let suffix = suffix.and_then(|s| { let s = s.as_str().get(); if ["f32", "f64"].contains(&s) { Some(s) } else { None } }).unwrap_or(""); self.bump(); let sp = lo.to(self.prev_span); let mut err = self.diagnostic() .struct_span_err(sp, "float literals must have an integer part"); err.span_suggestion( sp, "must have an integer part", format!("0.{}{}", val, suffix), Applicability::MachineApplicable, ); err.emit(); return Ok(match suffix { "f32" => ast::LitKind::Float(val, ast::FloatTy::F32), "f64" => ast::LitKind::Float(val, ast::FloatTy::F64), _ => ast::LitKind::FloatUnsuffixed(val), }); } else { unreachable!(); }; } _ => { return self.unexpected_last(&self.token); } }; self.bump(); Ok(out) } /// Matches `lit = true | false | token_lit`. crate fn parse_lit(&mut self) -> PResult<'a, Lit> { let lo = self.span; let lit = if self.eat_keyword(keywords::True) { LitKind::Bool(true) } else if self.eat_keyword(keywords::False) { LitKind::Bool(false) } else { let lit = self.parse_lit_token()?; lit }; Ok(source_map::Spanned { node: lit, span: lo.to(self.prev_span) }) } /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`). crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> { maybe_whole_expr!(self); let minus_lo = self.span; let minus_present = self.eat(&token::BinOp(token::Minus)); let lo = self.span; let literal = self.parse_lit()?; let hi = self.prev_span; let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new()); if minus_present { let minus_hi = self.prev_span; let unary = self.mk_unary(UnOp::Neg, expr); Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new())) } else { Ok(expr) } } fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> { match self.token { token::Ident(ident, _) if self.token.is_path_segment_keyword() => { let span = self.span; self.bump(); Ok(Ident::new(ident.name, span)) } _ => self.parse_ident(), } } fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> { match self.token { token::Ident(ident, false) if ident.name == keywords::Underscore.name() => { let span = self.span; self.bump(); Ok(Ident::new(ident.name, span)) } _ => self.parse_ident(), } } /// Parses a qualified path. /// Assumes that the leading `<` has been parsed already. /// /// `qualified_path = <type [as trait_ref]>::path` /// /// # Examples /// `<T>::default` /// `<T as U>::a` /// `<T as U>::F::a<S>` (without disambiguator) /// `<T as U>::F::a::<S>` (with disambiguator) fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> { let lo = self.prev_span; let ty = self.parse_ty()?; // `path` will contain the prefix of the path up to the `>`, // if any (e.g., `U` in the `<T as U>::*` examples // above). `path_span` has the span of that path, or an empty // span in the case of something like `<T>::Bar`. let (mut path, path_span); if self.eat_keyword(keywords::As) { let path_lo = self.span; path = self.parse_path(PathStyle::Type)?; path_span = path_lo.to(self.prev_span); } else { path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP }; path_span = self.span.to(self.span); } // See doc comment for `unmatched_angle_bracket_count`. self.expect(&token::Gt)?; if self.unmatched_angle_bracket_count > 0 { self.unmatched_angle_bracket_count -= 1; debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count); } self.expect(&token::ModSep)?; let qself = QSelf { ty, path_span, position: path.segments.len() }; self.parse_path_segments(&mut path.segments, style, true)?; Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) })) } /// Parses simple paths. /// /// `path = [::] segment+` /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]` /// /// # Examples /// `a::b::C<D>` (without disambiguator) /// `a::b::C::<D>` (with disambiguator) /// `Fn(Args)` (without disambiguator) /// `Fn::(Args)` (with disambiguator) pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> { self.parse_path_common(style, true) } crate fn parse_path_common(&mut self, style: PathStyle, enable_warning: bool) -> PResult<'a, ast::Path> { maybe_whole!(self, NtPath, |path| { if style == PathStyle::Mod && path.segments.iter().any(|segment| segment.args.is_some()) { self.diagnostic().span_err(path.span, "unexpected generic arguments in path"); } path }); let lo = self.meta_var_span.unwrap_or(self.span); let mut segments = Vec::new(); let mod_sep_ctxt = self.span.ctxt(); if self.eat(&token::ModSep) { segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))); } self.parse_path_segments(&mut segments, style, enable_warning)?; Ok(ast::Path { segments, span: lo.to(self.prev_span) }) } /// Like `parse_path`, but also supports parsing `Word` meta items into paths for /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]` /// attributes. pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> { let meta_ident = match self.token { token::Interpolated(ref nt) => match **nt { token::NtMeta(ref meta) => match meta.node { ast::MetaItemKind::Word => Some(meta.ident.clone()), _ => None, }, _ => None, }, _ => None, }; if let Some(path) = meta_ident { self.bump(); return Ok(path); } self.parse_path(style) } fn parse_path_segments(&mut self, segments: &mut Vec<PathSegment>, style: PathStyle, enable_warning: bool) -> PResult<'a, ()> { loop { let segment = self.parse_path_segment(style, enable_warning)?; if style == PathStyle::Expr { // In order to check for trailing angle brackets, we must have finished // recursing (`parse_path_segment` can indirectly call this function), // that is, the next token must be the highlighted part of the below example: // // `Foo::<Bar as Baz<T>>::Qux` // ^ here // // As opposed to the below highlight (if we had only finished the first // recursion): // // `Foo::<Bar as Baz<T>>::Qux` // ^ here // // `PathStyle::Expr` is only provided at the root invocation and never in // `parse_path_segment` to recurse and therefore can be checked to maintain // this invariant. self.check_trailing_angle_brackets(&segment, token::ModSep); } segments.push(segment); if self.is_import_coupler() || !self.eat(&token::ModSep) { return Ok(()); } } } fn parse_path_segment(&mut self, style: PathStyle, enable_warning: bool) -> PResult<'a, PathSegment> { let ident = self.parse_path_segment_ident()?; let is_args_start = |token: &token::Token| match *token { token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true, _ => false, }; let check_args_start = |this: &mut Self| { this.expected_tokens.extend_from_slice( &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))] ); is_args_start(&this.token) }; Ok(if style == PathStyle::Type && check_args_start(self) || style != PathStyle::Mod && self.check(&token::ModSep) && self.look_ahead(1, |t| is_args_start(t)) { // Generic arguments are found - `<`, `(`, `::<` or `::(`. if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning { self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator") .span_label(self.prev_span, "try removing `::`").emit(); } let lo = self.span; // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If // it isn't, then we reset the unmatched angle bracket count as we're about to start // parsing a new path. if style == PathStyle::Expr { self.unmatched_angle_bracket_count = 0; self.max_angle_bracket_count = 0; } let args = if self.eat_lt() { // `<'a, T, A = U>` let (args, bindings) = self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?; self.expect_gt()?; let span = lo.to(self.prev_span); AngleBracketedArgs { args, bindings, span }.into() } else { // `(T, U) -> R` self.bump(); // `(` let (inputs, recovered) = self.parse_seq_to_before_tokens( &[&token::CloseDelim(token::Paren)], SeqSep::trailing_allowed(token::Comma), TokenExpectType::Expect, |p| p.parse_ty())?; if !recovered { self.bump(); // `)` } let span = lo.to(self.prev_span); let output = if self.eat(&token::RArrow) { Some(self.parse_ty_common(false, false)?) } else { None }; ParenthesizedArgs { inputs, output, span }.into() }; PathSegment { ident, args, id: ast::DUMMY_NODE_ID } } else { // Generic arguments are not found. PathSegment::from_ident(ident) }) } crate fn check_lifetime(&mut self) -> bool { self.expected_tokens.push(TokenType::Lifetime); self.token.is_lifetime() } /// Parses a single lifetime `'a` or panics. crate fn expect_lifetime(&mut self) -> Lifetime { if let Some(ident) = self.token.lifetime() { let span = self.span; self.bump(); Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID } } else { self.span_bug(self.span, "not a lifetime") } } fn eat_label(&mut self) -> Option<Label> { if let Some(ident) = self.token.lifetime() { let span = self.span; self.bump(); Some(Label { ident: Ident::new(ident.name, span) }) } else { None } } /// Parses mutability (`mut` or nothing). fn parse_mutability(&mut self) -> Mutability { if self.eat_keyword(keywords::Mut) { Mutability::Mutable } else { Mutability::Immutable } } fn parse_field_name(&mut self) -> PResult<'a, Ident> { if let token::Literal(token::Integer(name), None) = self.token { self.bump(); Ok(Ident::new(name, self.prev_span)) } else { self.parse_ident_common(false) } } /// Parse ident (COLON expr)? fn parse_field(&mut self) -> PResult<'a, Field> { let attrs = self.parse_outer_attributes()?; let lo = self.span; // Check if a colon exists one ahead. This means we're parsing a fieldname. let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| { t == &token::Colon || t == &token::Eq }) { let fieldname = self.parse_field_name()?; // Check for an equals token. This means the source incorrectly attempts to // initialize a field with an eq rather than a colon. if self.token == token::Eq { self.diagnostic() .struct_span_err(self.span, "expected `:`, found `=`") .span_suggestion( fieldname.span.shrink_to_hi().to(self.span), "replace equals symbol with a colon", ":".to_string(), Applicability::MachineApplicable, ) .emit(); } self.bump(); // `:` (fieldname, self.parse_expr()?, false) } else { let fieldname = self.parse_ident_common(false)?; // Mimic `x: x` for the `x` field shorthand. let path = ast::Path::from_ident(fieldname); let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new()); (fieldname, expr, true) }; Ok(ast::Field { ident: fieldname, span: lo.to(expr.span), expr, is_shorthand, attrs: attrs.into(), }) } fn mk_expr(&mut self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> { P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID }) } fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind { ExprKind::Unary(unop, expr) } fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind { ExprKind::Binary(binop, lhs, rhs) } fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind { ExprKind::Call(f, args) } fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind { ExprKind::Index(expr, idx) } fn mk_range(&mut self, start: Option<P<Expr>>, end: Option<P<Expr>>, limits: RangeLimits) -> PResult<'a, ast::ExprKind> { if end.is_none() && limits == RangeLimits::Closed { Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd)) } else { Ok(ExprKind::Range(start, end, limits)) } } fn mk_assign_op(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind { ExprKind::AssignOp(binop, lhs, rhs) } pub fn mk_mac_expr(&mut self, span: Span, m: Mac_, attrs: ThinVec<Attribute>) -> P<Expr> { P(Expr { id: ast::DUMMY_NODE_ID, node: ExprKind::Mac(source_map::Spanned {node: m, span: span}), span, attrs, }) } fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> { let delim = match self.token { token::OpenDelim(delim) => delim, _ => { let msg = "expected open delimiter"; let mut err = self.fatal(msg); err.span_label(self.span, msg); return Err(err) } }; let tts = match self.parse_token_tree() { TokenTree::Delimited(_, _, tts) => tts, _ => unreachable!(), }; let delim = match delim { token::Paren => MacDelimiter::Parenthesis, token::Bracket => MacDelimiter::Bracket, token::Brace => MacDelimiter::Brace, token::NoDelim => self.bug("unexpected no delimiter"), }; Ok((delim, tts.into())) } /// At the bottom (top?) of the precedence hierarchy, /// Parses things like parenthesized exprs, macros, `return`, etc. /// /// N.B., this does not parse outer attributes, and is private because it only works /// correctly if called from `parse_dot_or_call_expr()`. fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> { maybe_whole_expr!(self); // Outer attributes are already parsed and will be // added to the return value after the fact. // // Therefore, prevent sub-parser from parsing // attributes by giving them a empty "already parsed" list. let mut attrs = ThinVec::new(); let lo = self.span; let mut hi = self.span; let ex: ExprKind; // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr(). match self.token { token::OpenDelim(token::Paren) => { self.bump(); attrs.extend(self.parse_inner_attributes()?); // (e) is parenthesized e // (e,) is a tuple with only one field, e let mut es = vec![]; let mut trailing_comma = false; let mut recovered = false; while self.token != token::CloseDelim(token::Paren) { es.push(self.parse_expr()?); recovered = self.expect_one_of( &[], &[token::Comma, token::CloseDelim(token::Paren)], )?; if self.eat(&token::Comma) { trailing_comma = true; } else { trailing_comma = false; break; } } if !recovered { self.bump(); } hi = self.prev_span; ex = if es.len() == 1 && !trailing_comma { ExprKind::Paren(es.into_iter().nth(0).unwrap()) } else { ExprKind::Tup(es) }; } token::OpenDelim(token::Brace) => { return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs); } token::BinOp(token::Or) | token::OrOr => { return self.parse_lambda_expr(attrs); } token::OpenDelim(token::Bracket) => { self.bump(); attrs.extend(self.parse_inner_attributes()?); if self.eat(&token::CloseDelim(token::Bracket)) { // Empty vector. ex = ExprKind::Array(Vec::new()); } else { // Nonempty vector. let first_expr = self.parse_expr()?; if self.eat(&token::Semi) { // Repeating array syntax: [ 0; 512 ] let count = AnonConst { id: ast::DUMMY_NODE_ID, value: self.parse_expr()?, }; self.expect(&token::CloseDelim(token::Bracket))?; ex = ExprKind::Repeat(first_expr, count); } else if self.eat(&token::Comma) { // Vector with two or more elements. let remaining_exprs = self.parse_seq_to_end( &token::CloseDelim(token::Bracket), SeqSep::trailing_allowed(token::Comma), |p| Ok(p.parse_expr()?) )?; let mut exprs = vec![first_expr]; exprs.extend(remaining_exprs); ex = ExprKind::Array(exprs); } else { // Vector with one element. self.expect(&token::CloseDelim(token::Bracket))?; ex = ExprKind::Array(vec![first_expr]); } } hi = self.prev_span; } _ => { if self.eat_lt() { let (qself, path) = self.parse_qpath(PathStyle::Expr)?; hi = path.span; return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs)); } if self.span.rust_2018() && self.check_keyword(keywords::Async) { if self.is_async_block() { // check for `async {` and `async move {` return self.parse_async_block(attrs); } else { return self.parse_lambda_expr(attrs); } } if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) { return self.parse_lambda_expr(attrs); } if self.eat_keyword(keywords::If) { return self.parse_if_expr(attrs); } if self.eat_keyword(keywords::For) { let lo = self.prev_span; return self.parse_for_expr(None, lo, attrs); } if self.eat_keyword(keywords::While) { let lo = self.prev_span; return self.parse_while_expr(None, lo, attrs); } if let Some(label) = self.eat_label() { let lo = label.ident.span; self.expect(&token::Colon)?; if self.eat_keyword(keywords::While) { return self.parse_while_expr(Some(label), lo, attrs) } if self.eat_keyword(keywords::For) { return self.parse_for_expr(Some(label), lo, attrs) } if self.eat_keyword(keywords::Loop) { return self.parse_loop_expr(Some(label), lo, attrs) } if self.token == token::OpenDelim(token::Brace) { return self.parse_block_expr(Some(label), lo, BlockCheckMode::Default, attrs); } let msg = "expected `while`, `for`, `loop` or `{` after a label"; let mut err = self.fatal(msg); err.span_label(self.span, msg); return Err(err); } if self.eat_keyword(keywords::Loop) { let lo = self.prev_span; return self.parse_loop_expr(None, lo, attrs); } if self.eat_keyword(keywords::Continue) { let label = self.eat_label(); let ex = ExprKind::Continue(label); let hi = self.prev_span; return Ok(self.mk_expr(lo.to(hi), ex, attrs)); } if self.eat_keyword(keywords::Match) { let match_sp = self.prev_span; return self.parse_match_expr(attrs).map_err(|mut err| { err.span_label(match_sp, "while parsing this match expression"); err }); } if self.eat_keyword(keywords::Unsafe) { return self.parse_block_expr( None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs); } if self.is_do_catch_block() { let mut db = self.fatal("found removed `do catch` syntax"); db.help("Following RFC #2388, the new non-placeholder syntax is `try`"); return Err(db); } if self.is_try_block() { let lo = self.span; assert!(self.eat_keyword(keywords::Try)); return self.parse_try_block(lo, attrs); } if self.eat_keyword(keywords::Return) { if self.token.can_begin_expr() { let e = self.parse_expr()?; hi = e.span; ex = ExprKind::Ret(Some(e)); } else { ex = ExprKind::Ret(None); } } else if self.eat_keyword(keywords::Break) { let label = self.eat_label(); let e = if self.token.can_begin_expr() && !(self.token == token::OpenDelim(token::Brace) && self.restrictions.contains( Restrictions::NO_STRUCT_LITERAL)) { Some(self.parse_expr()?) } else { None }; ex = ExprKind::Break(label, e); hi = self.prev_span; } else if self.eat_keyword(keywords::Yield) { if self.token.can_begin_expr() { let e = self.parse_expr()?; hi = e.span; ex = ExprKind::Yield(Some(e)); } else { ex = ExprKind::Yield(None); } } else if self.token.is_keyword(keywords::Let) { // Catch this syntax error here, instead of in `parse_ident`, so // that we can explicitly mention that let is not to be used as an expression let mut db = self.fatal("expected expression, found statement (`let`)"); db.span_label(self.span, "expected expression"); db.note("variable declaration using `let` is a statement"); return Err(db); } else if self.token.is_path_start() { let pth = self.parse_path(PathStyle::Expr)?; // `!`, as an operator, is prefix, so we know this isn't that if self.eat(&token::Not) { // MACRO INVOCATION expression let (delim, tts) = self.expect_delimited_token_tree()?; let hi = self.prev_span; let node = Mac_ { path: pth, tts, delim }; return Ok(self.mk_mac_expr(lo.to(hi), node, attrs)) } if self.check(&token::OpenDelim(token::Brace)) { // This is a struct literal, unless we're prohibited // from parsing struct literals here. let prohibited = self.restrictions.contains( Restrictions::NO_STRUCT_LITERAL ); if !prohibited { return self.parse_struct_expr(lo, pth, attrs); } } hi = pth.span; ex = ExprKind::Path(None, pth); } else { if !self.unclosed_delims.is_empty() && self.check(&token::Semi) { // Don't complain about bare semicolons after unclosed braces // recovery in order to keep the error count down. Fixing the // delimiters will possibly also fix the bare semicolon found in // expression context. For example, silence the following error: // ``` // error: expected expression, found `;` // --> file.rs:2:13 // | // 2 | foo(bar(; // | ^ expected expression // ``` self.bump(); return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new())); } match self.parse_literal_maybe_minus() { Ok(expr) => { hi = expr.span; ex = expr.node.clone(); } Err(mut err) => { self.cancel(&mut err); let msg = format!("expected expression, found {}", self.this_token_descr()); let mut err = self.fatal(&msg); err.span_label(self.span, "expected expression"); return Err(err); } } } } } let expr = Expr { node: ex, span: lo.to(hi), id: ast::DUMMY_NODE_ID, attrs }; let expr = self.maybe_recover_from_bad_qpath(expr, true)?; return Ok(P(expr)); } fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { let struct_sp = lo.to(self.prev_span); self.bump(); let mut fields = Vec::new(); let mut base = None; attrs.extend(self.parse_inner_attributes()?); while self.token != token::CloseDelim(token::Brace) { if self.eat(&token::DotDot) { let exp_span = self.prev_span; match self.parse_expr() { Ok(e) => { base = Some(e); } Err(mut e) => { e.emit(); self.recover_stmt(); } } if self.token == token::Comma { let mut err = self.sess.span_diagnostic.mut_span_err( exp_span.to(self.prev_span), "cannot use a comma after the base struct", ); err.span_suggestion_short( self.span, "remove this comma", String::new(), Applicability::MachineApplicable ); err.note("the base struct must always be the last field"); err.emit(); self.recover_stmt(); } break; } let mut recovery_field = None; if let token::Ident(ident, _) = self.token { if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) { // Use in case of error after field-looking code: `S { foo: () with a }` let mut ident = ident.clone(); ident.span = self.span; recovery_field = Some(ast::Field { ident, span: self.span, expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()), is_shorthand: false, attrs: ThinVec::new(), }); } } let mut parsed_field = None; match self.parse_field() { Ok(f) => parsed_field = Some(f), Err(mut e) => { e.span_label(struct_sp, "while parsing this struct"); e.emit(); // If the next token is a comma, then try to parse // what comes next as additional fields, rather than // bailing out until next `}`. if self.token != token::Comma { self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore); if self.token != token::Comma { break; } } } } match self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) { Ok(_) => if let Some(f) = parsed_field.or(recovery_field) { // only include the field if there's no parse error for the field name fields.push(f); } Err(mut e) => { if let Some(f) = recovery_field { fields.push(f); } e.span_label(struct_sp, "while parsing this struct"); e.emit(); self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore); self.eat(&token::Comma); } } } let span = lo.to(self.span); self.expect(&token::CloseDelim(token::Brace))?; return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs)); } fn parse_or_use_outer_attributes(&mut self, already_parsed_attrs: Option<ThinVec<Attribute>>) -> PResult<'a, ThinVec<Attribute>> { if let Some(attrs) = already_parsed_attrs { Ok(attrs) } else { self.parse_outer_attributes().map(|a| a.into()) } } /// Parses a block or unsafe block. fn parse_block_expr(&mut self, opt_label: Option<Label>, lo: Span, blk_mode: BlockCheckMode, outer_attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { self.expect(&token::OpenDelim(token::Brace))?; let mut attrs = outer_attrs; attrs.extend(self.parse_inner_attributes()?); let blk = self.parse_block_tail(lo, blk_mode)?; return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs)); } /// Parses `a.b` or `a(13)` or `a[4]` or just `a`. fn parse_dot_or_call_expr(&mut self, already_parsed_attrs: Option<ThinVec<Attribute>>) -> PResult<'a, P<Expr>> { let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?; let b = self.parse_bottom_expr(); let (span, b) = self.interpolated_or_expr_span(b)?; self.parse_dot_or_call_expr_with(b, span, attrs) } fn parse_dot_or_call_expr_with(&mut self, e0: P<Expr>, lo: Span, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { // Stitch the list of outer attributes onto the return value. // A little bit ugly, but the best way given the current code // structure self.parse_dot_or_call_expr_with_(e0, lo) .map(|expr| expr.map(|mut expr| { attrs.extend::<Vec<_>>(expr.attrs.into()); expr.attrs = attrs; match expr.node { ExprKind::If(..) | ExprKind::IfLet(..) => { if !expr.attrs.is_empty() { // Just point to the first attribute in there... let span = expr.attrs[0].span; self.span_err(span, "attributes are not yet allowed on `if` \ expressions"); } } _ => {} } expr }) ) } // Assuming we have just parsed `.`, continue parsing into an expression. fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> { let segment = self.parse_path_segment(PathStyle::Expr, true)?; self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren)); Ok(match self.token { token::OpenDelim(token::Paren) => { // Method call `expr.f()` let mut args = self.parse_unspanned_seq( &token::OpenDelim(token::Paren), &token::CloseDelim(token::Paren), SeqSep::trailing_allowed(token::Comma), |p| Ok(p.parse_expr()?) )?; args.insert(0, self_arg); let span = lo.to(self.prev_span); self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new()) } _ => { // Field access `expr.f` if let Some(args) = segment.args { self.span_err(args.span(), "field expressions may not have generic arguments"); } let span = lo.to(self.prev_span); self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new()) } }) } /// This function checks if there are trailing angle brackets and produces /// a diagnostic to suggest removing them. /// /// ```ignore (diagnostic) /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>(); /// ^^ help: remove extra angle brackets /// ``` fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) { // This function is intended to be invoked after parsing a path segment where there are two // cases: // // 1. A specific token is expected after the path segment. // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call), // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path). // 2. No specific token is expected after the path segment. // eg. `x.foo` (field access) // // This function is called after parsing `.foo` and before parsing the token `end` (if // present). This includes any angle bracket arguments, such as `.foo::<u32>` or // `Foo::<Bar>`. // We only care about trailing angle brackets if we previously parsed angle bracket // arguments. This helps stop us incorrectly suggesting that extra angle brackets be // removed in this case: // // `x.foo >> (3)` (where `x.foo` is a `u32` for example) // // This case is particularly tricky as we won't notice it just looking at the tokens - // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will // have already been parsed): // // `x.foo::<u32>>>(3)` let parsed_angle_bracket_args = segment.args .as_ref() .map(|args| args.is_angle_bracketed()) .unwrap_or(false); debug!( "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}", parsed_angle_bracket_args, ); if !parsed_angle_bracket_args { return; } // Keep the span at the start so we can highlight the sequence of `>` characters to be // removed. let lo = self.span; // We need to look-ahead to see if we have `>` characters without moving the cursor forward // (since we might have the field access case and the characters we're eating are // actual operators and not trailing characters - ie `x.foo >> 3`). let mut position = 0; // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how // many of each (so we can correctly pluralize our error messages) and continue to // advance. let mut number_of_shr = 0; let mut number_of_gt = 0; while self.look_ahead(position, |t| { trace!("check_trailing_angle_brackets: t={:?}", t); if *t == token::BinOp(token::BinOpToken::Shr) { number_of_shr += 1; true } else if *t == token::Gt { number_of_gt += 1; true } else { false } }) { position += 1; } // If we didn't find any trailing `>` characters, then we have nothing to error about. debug!( "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}", number_of_gt, number_of_shr, ); if number_of_gt < 1 && number_of_shr < 1 { return; } // Finally, double check that we have our end token as otherwise this is the // second case. if self.look_ahead(position, |t| { trace!("check_trailing_angle_brackets: t={:?}", t); *t == end }) { // Eat from where we started until the end token so that parsing can continue // as if we didn't have those extra angle brackets. self.eat_to_tokens(&[&end]); let span = lo.until(self.span); let plural = number_of_gt > 1 || number_of_shr >= 1; self.diagnostic() .struct_span_err( span, &format!("unmatched angle bracket{}", if plural { "s" } else { "" }), ) .span_suggestion( span, &format!("remove extra angle bracket{}", if plural { "s" } else { "" }), String::new(), Applicability::MachineApplicable, ) .emit(); } } fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> { let mut e = e0; let mut hi; loop { // expr? while self.eat(&token::Question) { let hi = self.prev_span; e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new()); } // expr.f if self.eat(&token::Dot) { match self.token { token::Ident(..) => { e = self.parse_dot_suffix(e, lo)?; } token::Literal(token::Integer(name), _) => { let span = self.span; self.bump(); let field = ExprKind::Field(e, Ident::new(name, span)); e = self.mk_expr(lo.to(span), field, ThinVec::new()); } token::Literal(token::Float(n), _suf) => { self.bump(); let fstr = n.as_str(); let mut err = self.diagnostic() .struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n)); err.span_label(self.prev_span, "unexpected token"); if fstr.chars().all(|x| "0123456789.".contains(x)) { let float = match fstr.parse::<f64>().ok() { Some(f) => f, None => continue, }; let sugg = pprust::to_string(|s| { use crate::print::pprust::PrintState; s.popen()?; s.print_expr(&e)?; s.s.word( ".")?; s.print_usize(float.trunc() as usize)?; s.pclose()?; s.s.word(".")?; s.s.word(fstr.splitn(2, ".").last().unwrap().to_string()) }); err.span_suggestion( lo.to(self.prev_span), "try parenthesizing the first index", sugg, Applicability::MachineApplicable ); } return Err(err); } _ => { // FIXME Could factor this out into non_fatal_unexpected or something. let actual = self.this_token_to_string(); self.span_err(self.span, &format!("unexpected token: `{}`", actual)); } } continue; } if self.expr_is_complete(&e) { break; } match self.token { // expr(...) token::OpenDelim(token::Paren) => { let es = self.parse_unspanned_seq( &token::OpenDelim(token::Paren), &token::CloseDelim(token::Paren), SeqSep::trailing_allowed(token::Comma), |p| Ok(p.parse_expr()?) )?; hi = self.prev_span; let nd = self.mk_call(e, es); e = self.mk_expr(lo.to(hi), nd, ThinVec::new()); } // expr[...] // Could be either an index expression or a slicing expression. token::OpenDelim(token::Bracket) => { self.bump(); let ix = self.parse_expr()?; hi = self.span; self.expect(&token::CloseDelim(token::Bracket))?; let index = self.mk_index(e, ix); e = self.mk_expr(lo.to(hi), index, ThinVec::new()) } _ => return Ok(e) } } return Ok(e); } crate fn process_potential_macro_variable(&mut self) { let (token, span) = match self.token { token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() && self.look_ahead(1, |t| t.is_ident()) => { self.bump(); let name = match self.token { token::Ident(ident, _) => ident, _ => unreachable!() }; let mut err = self.fatal(&format!("unknown macro variable `{}`", name)); err.span_label(self.span, "unknown macro variable"); err.emit(); self.bump(); return } token::Interpolated(ref nt) => { self.meta_var_span = Some(self.span); // Interpolated identifier and lifetime tokens are replaced with usual identifier // and lifetime tokens, so the former are never encountered during normal parsing. match **nt { token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span), token::NtLifetime(ident) => (token::Lifetime(ident), ident.span), _ => return, } } _ => return, }; self.token = token; self.span = span; } /// Parses a single token tree from the input. crate fn parse_token_tree(&mut self) -> TokenTree { match self.token { token::OpenDelim(..) => { let frame = mem::replace(&mut self.token_cursor.frame, self.token_cursor.stack.pop().unwrap()); self.span = frame.span.entire(); self.bump(); TokenTree::Delimited( frame.span, frame.delim, frame.tree_cursor.stream.into(), ) }, token::CloseDelim(_) | token::Eof => unreachable!(), _ => { let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span); self.bump(); TokenTree::Token(span, token) } } } // parse a stream of tokens into a list of TokenTree's, // up to EOF. pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> { let mut tts = Vec::new(); while self.token != token::Eof { tts.push(self.parse_token_tree()); } Ok(tts) } pub fn parse_tokens(&mut self) -> TokenStream { let mut result = Vec::new(); loop { match self.token { token::Eof | token::CloseDelim(..) => break, _ => result.push(self.parse_token_tree().into()), } } TokenStream::new(result) } /// Parse a prefix-unary-operator expr fn parse_prefix_expr(&mut self, already_parsed_attrs: Option<ThinVec<Attribute>>) -> PResult<'a, P<Expr>> { let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?; let lo = self.span; // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr() let (hi, ex) = match self.token { token::Not => { self.bump(); let e = self.parse_prefix_expr(None); let (span, e) = self.interpolated_or_expr_span(e)?; (lo.to(span), self.mk_unary(UnOp::Not, e)) } // Suggest `!` for bitwise negation when encountering a `~` token::Tilde => { self.bump(); let e = self.parse_prefix_expr(None); let (span, e) = self.interpolated_or_expr_span(e)?; let span_of_tilde = lo; let mut err = self.diagnostic() .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator"); err.span_suggestion_short( span_of_tilde, "use `!` to perform bitwise negation", "!".to_owned(), Applicability::MachineApplicable ); err.emit(); (lo.to(span), self.mk_unary(UnOp::Not, e)) } token::BinOp(token::Minus) => { self.bump(); let e = self.parse_prefix_expr(None); let (span, e) = self.interpolated_or_expr_span(e)?; (lo.to(span), self.mk_unary(UnOp::Neg, e)) } token::BinOp(token::Star) => { self.bump(); let e = self.parse_prefix_expr(None); let (span, e) = self.interpolated_or_expr_span(e)?; (lo.to(span), self.mk_unary(UnOp::Deref, e)) } token::BinOp(token::And) | token::AndAnd => { self.expect_and()?; let m = self.parse_mutability(); let e = self.parse_prefix_expr(None); let (span, e) = self.interpolated_or_expr_span(e)?; (lo.to(span), ExprKind::AddrOf(m, e)) } token::Ident(..) if self.token.is_keyword(keywords::In) => { self.bump(); let place = self.parse_expr_res( Restrictions::NO_STRUCT_LITERAL, None, )?; let blk = self.parse_block()?; let span = blk.span; let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new()); (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr)) } token::Ident(..) if self.token.is_keyword(keywords::Box) => { self.bump(); let e = self.parse_prefix_expr(None); let (span, e) = self.interpolated_or_expr_span(e)?; (lo.to(span), ExprKind::Box(e)) } token::Ident(..) if self.token.is_ident_named("not") => { // `not` is just an ordinary identifier in Rust-the-language, // but as `rustc`-the-compiler, we can issue clever diagnostics // for confused users who really want to say `!` let token_cannot_continue_expr = |t: &token::Token| match *t { // These tokens can start an expression after `!`, but // can't continue an expression after an ident token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw), token::Literal(..) | token::Pound => true, token::Interpolated(ref nt) => match **nt { token::NtIdent(..) | token::NtExpr(..) | token::NtBlock(..) | token::NtPath(..) => true, _ => false, }, _ => false }; let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr); if cannot_continue_expr { self.bump(); // Emit the error ... let mut err = self.diagnostic() .struct_span_err(self.span, &format!("unexpected {} after identifier", self.this_token_descr())); // span the `not` plus trailing whitespace to avoid // trailing whitespace after the `!` in our suggestion let to_replace = self.sess.source_map() .span_until_non_whitespace(lo.to(self.span)); err.span_suggestion_short( to_replace, "use `!` to perform logical negation", "!".to_owned(), Applicability::MachineApplicable ); err.emit(); // —and recover! (just as if we were in the block // for the `token::Not` arm) let e = self.parse_prefix_expr(None); let (span, e) = self.interpolated_or_expr_span(e)?; (lo.to(span), self.mk_unary(UnOp::Not, e)) } else { return self.parse_dot_or_call_expr(Some(attrs)); } } _ => { return self.parse_dot_or_call_expr(Some(attrs)); } }; return Ok(self.mk_expr(lo.to(hi), ex, attrs)); } /// Parses an associative expression. /// /// This parses an expression accounting for associativity and precedence of the operators in /// the expression. #[inline] fn parse_assoc_expr(&mut self, already_parsed_attrs: Option<ThinVec<Attribute>>) -> PResult<'a, P<Expr>> { self.parse_assoc_expr_with(0, already_parsed_attrs.into()) } /// Parses an associative expression with operators of at least `min_prec` precedence. fn parse_assoc_expr_with(&mut self, min_prec: usize, lhs: LhsExpr) -> PResult<'a, P<Expr>> { let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs { expr } else { let attrs = match lhs { LhsExpr::AttributesParsed(attrs) => Some(attrs), _ => None, }; if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) { return self.parse_prefix_range_expr(attrs); } else { self.parse_prefix_expr(attrs)? } }; if self.expr_is_complete(&lhs) { // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071 return Ok(lhs); } self.expected_tokens.push(TokenType::Operator); while let Some(op) = AssocOp::from_token(&self.token) { // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what // it refers to. Interpolated identifiers are unwrapped early and never show up here // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process // it as "interpolated", it doesn't change the answer for non-interpolated idents. let lhs_span = match (self.prev_token_kind, &lhs.node) { (PrevTokenKind::Interpolated, _) => self.prev_span, (PrevTokenKind::Ident, &ExprKind::Path(None, ref path)) if path.segments.len() == 1 => self.prev_span, _ => lhs.span, }; let cur_op_span = self.span; let restrictions = if op.is_assign_like() { self.restrictions & Restrictions::NO_STRUCT_LITERAL } else { self.restrictions }; if op.precedence() < min_prec { break; } // Check for deprecated `...` syntax if self.token == token::DotDotDot && op == AssocOp::DotDotEq { self.err_dotdotdot_syntax(self.span); } self.bump(); if op.is_comparison() { self.check_no_chained_comparison(&lhs, &op); } // Special cases: if op == AssocOp::As { lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?; continue } else if op == AssocOp::Colon { lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) { Ok(lhs) => lhs, Err(mut err) => { err.span_label(self.span, "expecting a type here because of type ascription"); let cm = self.sess.source_map(); let cur_pos = cm.lookup_char_pos(self.span.lo()); let op_pos = cm.lookup_char_pos(cur_op_span.hi()); if cur_pos.line != op_pos.line { err.span_suggestion( cur_op_span, "try using a semicolon", ";".to_string(), Applicability::MaybeIncorrect // speculative ); } return Err(err); } }; continue } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq { // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to // generalise it to the Fixity::None code. // // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other // two variants are handled with `parse_prefix_range_expr` call above. let rhs = if self.is_at_start_of_range_notation_rhs() { Some(self.parse_assoc_expr_with(op.precedence() + 1, LhsExpr::NotYetParsed)?) } else { None }; let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs { x.span } else { cur_op_span }); let limits = if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed }; let r = self.mk_range(Some(lhs), rhs, limits)?; lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new()); break } let rhs = match op.fixity() { Fixity::Right => self.with_res( restrictions - Restrictions::STMT_EXPR, |this| { this.parse_assoc_expr_with(op.precedence(), LhsExpr::NotYetParsed) }), Fixity::Left => self.with_res( restrictions - Restrictions::STMT_EXPR, |this| { this.parse_assoc_expr_with(op.precedence() + 1, LhsExpr::NotYetParsed) }), // We currently have no non-associative operators that are not handled above by // the special cases. The code is here only for future convenience. Fixity::None => self.with_res( restrictions - Restrictions::STMT_EXPR, |this| { this.parse_assoc_expr_with(op.precedence() + 1, LhsExpr::NotYetParsed) }), }?; // Make sure that the span of the parent node is larger than the span of lhs and rhs, // including the attributes. let lhs_span = lhs .attrs .iter() .filter(|a| a.style == AttrStyle::Outer) .next() .map_or(lhs_span, |a| a.span); let span = lhs_span.to(rhs.span); lhs = match op { AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor | AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight | AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual | AssocOp::Greater | AssocOp::GreaterEqual => { let ast_op = op.to_ast_binop().unwrap(); let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs); self.mk_expr(span, binary, ThinVec::new()) } AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()), AssocOp::ObsoleteInPlace => self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()), AssocOp::AssignOp(k) => { let aop = match k { token::Plus => BinOpKind::Add, token::Minus => BinOpKind::Sub, token::Star => BinOpKind::Mul, token::Slash => BinOpKind::Div, token::Percent => BinOpKind::Rem, token::Caret => BinOpKind::BitXor, token::And => BinOpKind::BitAnd, token::Or => BinOpKind::BitOr, token::Shl => BinOpKind::Shl, token::Shr => BinOpKind::Shr, }; let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs); self.mk_expr(span, aopexpr, ThinVec::new()) } AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => { self.bug("AssocOp should have been handled by special case") } }; if op.fixity() == Fixity::None { break } } Ok(lhs) } fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span, expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind) -> PResult<'a, P<Expr>> { let mk_expr = |this: &mut Self, rhs: P<Ty>| { this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new()) }; // Save the state of the parser before parsing type normally, in case there is a // LessThan comparison after this cast. let parser_snapshot_before_type = self.clone(); match self.parse_ty_no_plus() { Ok(rhs) => { Ok(mk_expr(self, rhs)) } Err(mut type_err) => { // Rewind to before attempting to parse the type with generics, to recover // from situations like `x as usize < y` in which we first tried to parse // `usize < y` as a type with generic arguments. let parser_snapshot_after_type = self.clone(); mem::replace(self, parser_snapshot_before_type); match self.parse_path(PathStyle::Expr) { Ok(path) => { let (op_noun, op_verb) = match self.token { token::Lt => ("comparison", "comparing"), token::BinOp(token::Shl) => ("shift", "shifting"), _ => { // We can end up here even without `<` being the next token, for // example because `parse_ty_no_plus` returns `Err` on keywords, // but `parse_path` returns `Ok` on them due to error recovery. // Return original error and parser state. mem::replace(self, parser_snapshot_after_type); return Err(type_err); } }; // Successfully parsed the type path leaving a `<` yet to parse. type_err.cancel(); // Report non-fatal diagnostics, keep `x as usize` as an expression // in AST and continue parsing. let msg = format!("`<` is interpreted as a start of generic \ arguments for `{}`, not a {}", path, op_noun); let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg); err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span), "interpreted as generic arguments"); err.span_label(self.span, format!("not interpreted as {}", op_noun)); let expr = mk_expr(self, P(Ty { span: path.span, node: TyKind::Path(None, path), id: ast::DUMMY_NODE_ID })); let expr_str = self.sess.source_map().span_to_snippet(expr.span) .unwrap_or_else(|_| pprust::expr_to_string(&expr)); err.span_suggestion( expr.span, &format!("try {} the cast value", op_verb), format!("({})", expr_str), Applicability::MachineApplicable ); err.emit(); Ok(expr) } Err(mut path_err) => { // Couldn't parse as a path, return original error and parser state. path_err.cancel(); mem::replace(self, parser_snapshot_after_type); Err(type_err) } } } } } /// Produce an error if comparison operators are chained (RFC #558). /// We only need to check lhs, not rhs, because all comparison ops /// have same precedence and are left-associative fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) { debug_assert!(outer_op.is_comparison(), "check_no_chained_comparison: {:?} is not comparison", outer_op); match lhs.node { ExprKind::Binary(op, _, _) if op.node.is_comparison() => { // respan to include both operators let op_span = op.span.to(self.span); let mut err = self.diagnostic().struct_span_err(op_span, "chained comparison operators require parentheses"); if op.node == BinOpKind::Lt && *outer_op == AssocOp::Less || // Include `<` to provide this recommendation *outer_op == AssocOp::Greater // even in a case like the following: { // Foo<Bar<Baz<Qux, ()>>> err.help( "use `::<...>` instead of `<...>` if you meant to specify type arguments"); err.help("or use `(...)` if you meant to specify fn arguments"); } err.emit(); } _ => {} } } /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr` fn parse_prefix_range_expr(&mut self, already_parsed_attrs: Option<ThinVec<Attribute>>) -> PResult<'a, P<Expr>> { // Check for deprecated `...` syntax if self.token == token::DotDotDot { self.err_dotdotdot_syntax(self.span); } debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token), "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq", self.token); let tok = self.token.clone(); let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?; let lo = self.span; let mut hi = self.span; self.bump(); let opt_end = if self.is_at_start_of_range_notation_rhs() { // RHS must be parsed with more associativity than the dots. let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1; Some(self.parse_assoc_expr_with(next_prec, LhsExpr::NotYetParsed) .map(|x|{ hi = x.span; x })?) } else { None }; let limits = if tok == token::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed }; let r = self.mk_range(None, opt_end, limits)?; Ok(self.mk_expr(lo.to(hi), r, attrs)) } fn is_at_start_of_range_notation_rhs(&self) -> bool { if self.token.can_begin_expr() { // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`. if self.token == token::OpenDelim(token::Brace) { return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL); } true } else { false } } /// Parses an `if` or `if let` expression (`if` token already eaten). fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { if self.check_keyword(keywords::Let) { return self.parse_if_let_expr(attrs); } let lo = self.prev_span; let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then // verify that the last statement is either an implicit return (no `;`) or an explicit // return. This won't catch blocks with an explicit `return`, but that would be caught by // the dead code lint. if self.eat_keyword(keywords::Else) || !cond.returns() { let sp = self.sess.source_map().next_point(lo); let mut err = self.diagnostic() .struct_span_err(sp, "missing condition for `if` statement"); err.span_label(sp, "expected if condition here"); return Err(err) } let not_block = self.token != token::OpenDelim(token::Brace); let thn = self.parse_block().map_err(|mut err| { if not_block { err.span_label(lo, "this `if` statement has a condition, but no block"); } err })?; let mut els: Option<P<Expr>> = None; let mut hi = thn.span; if self.eat_keyword(keywords::Else) { let elexpr = self.parse_else_expr()?; hi = elexpr.span; els = Some(elexpr); } Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs)) } /// Parses an `if let` expression (`if` token already eaten). fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { let lo = self.prev_span; self.expect_keyword(keywords::Let)?; let pats = self.parse_pats()?; self.expect(&token::Eq)?; let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; let thn = self.parse_block()?; let (hi, els) = if self.eat_keyword(keywords::Else) { let expr = self.parse_else_expr()?; (expr.span, Some(expr)) } else { (thn.span, None) }; Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs)) } /// Parses `move |args| expr`. fn parse_lambda_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { let lo = self.span; let movability = if self.eat_keyword(keywords::Static) { Movability::Static } else { Movability::Movable }; let asyncness = if self.span.rust_2018() { self.parse_asyncness() } else { IsAsync::NotAsync }; let capture_clause = if self.eat_keyword(keywords::Move) { CaptureBy::Value } else { CaptureBy::Ref }; let decl = self.parse_fn_block_decl()?; let decl_hi = self.prev_span; let body = match decl.output { FunctionRetTy::Default(_) => { let restrictions = self.restrictions - Restrictions::STMT_EXPR; self.parse_expr_res(restrictions, None)? }, _ => { // If an explicit return type is given, require a // block to appear (RFC 968). let body_lo = self.span; self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())? } }; Ok(self.mk_expr( lo.to(body.span), ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)), attrs)) } // `else` token already eaten fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> { if self.eat_keyword(keywords::If) { return self.parse_if_expr(ThinVec::new()); } else { let blk = self.parse_block()?; return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new())); } } /// Parse a 'for' .. 'in' expression ('for' token already eaten) fn parse_for_expr(&mut self, opt_label: Option<Label>, span_lo: Span, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { // Parse: `for <src_pat> in <src_expr> <src_loop_block>` let pat = self.parse_top_level_pat()?; if !self.eat_keyword(keywords::In) { let in_span = self.prev_span.between(self.span); let mut err = self.sess.span_diagnostic .struct_span_err(in_span, "missing `in` in `for` loop"); err.span_suggestion_short( in_span, "try adding `in` here", " in ".into(), // has been misleading, at least in the past (closed Issue #48492) Applicability::MaybeIncorrect ); err.emit(); } let in_span = self.prev_span; if self.eat_keyword(keywords::In) { // a common typo: `for _ in in bar {}` let mut err = self.sess.span_diagnostic.struct_span_err( self.prev_span, "expected iterable, found keyword `in`", ); err.span_suggestion_short( in_span.until(self.prev_span), "remove the duplicated `in`", String::new(), Applicability::MachineApplicable, ); err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)"); err.note("for more information on the status of emplacement syntax, see <\ https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>"); err.emit(); } let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?; attrs.extend(iattrs); let hi = self.prev_span; Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs)) } /// Parses a `while` or `while let` expression (`while` token already eaten). fn parse_while_expr(&mut self, opt_label: Option<Label>, span_lo: Span, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { if self.token.is_keyword(keywords::Let) { return self.parse_while_let_expr(opt_label, span_lo, attrs); } let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; let (iattrs, body) = self.parse_inner_attrs_and_block()?; attrs.extend(iattrs); let span = span_lo.to(body.span); return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs)); } /// Parses a `while let` expression (`while` token already eaten). fn parse_while_let_expr(&mut self, opt_label: Option<Label>, span_lo: Span, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { self.expect_keyword(keywords::Let)?; let pats = self.parse_pats()?; self.expect(&token::Eq)?; let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; let (iattrs, body) = self.parse_inner_attrs_and_block()?; attrs.extend(iattrs); let span = span_lo.to(body.span); return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs)); } // parse `loop {...}`, `loop` token already eaten fn parse_loop_expr(&mut self, opt_label: Option<Label>, span_lo: Span, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { let (iattrs, body) = self.parse_inner_attrs_and_block()?; attrs.extend(iattrs); let span = span_lo.to(body.span); Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs)) } /// Parses an `async move {...}` expression. pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { let span_lo = self.span; self.expect_keyword(keywords::Async)?; let capture_clause = if self.eat_keyword(keywords::Move) { CaptureBy::Value } else { CaptureBy::Ref }; let (iattrs, body) = self.parse_inner_attrs_and_block()?; attrs.extend(iattrs); Ok(self.mk_expr( span_lo.to(body.span), ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs)) } /// Parses a `try {...}` expression (`try` token already eaten). fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { let (iattrs, body) = self.parse_inner_attrs_and_block()?; attrs.extend(iattrs); Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs)) } // `match` token already eaten fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { let match_span = self.prev_span; let lo = self.prev_span; let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) { if self.token == token::Token::Semi { e.span_suggestion_short( match_span, "try removing this `match`", String::new(), Applicability::MaybeIncorrect // speculative ); } return Err(e) } attrs.extend(self.parse_inner_attributes()?); let mut arms: Vec<Arm> = Vec::new(); while self.token != token::CloseDelim(token::Brace) { match self.parse_arm() { Ok(arm) => arms.push(arm), Err(mut e) => { // Recover by skipping to the end of the block. e.emit(); self.recover_stmt(); let span = lo.to(self.span); if self.token == token::CloseDelim(token::Brace) { self.bump(); } return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs)); } } } let hi = self.span; self.bump(); return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs)); } crate fn parse_arm(&mut self) -> PResult<'a, Arm> { maybe_whole!(self, NtArm, |x| x); let attrs = self.parse_outer_attributes()?; let pats = self.parse_pats()?; let guard = if self.eat_keyword(keywords::If) { Some(Guard::If(self.parse_expr()?)) } else { None }; let arrow_span = self.span; self.expect(&token::FatArrow)?; let arm_start_span = self.span; let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None) .map_err(|mut err| { err.span_label(arrow_span, "while parsing the `match` arm starting here"); err })?; let require_comma = classify::expr_requires_semi_to_be_stmt(&expr) && self.token != token::CloseDelim(token::Brace); if require_comma { let cm = self.sess.source_map(); self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) .map_err(|mut err| { match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) { (Ok(ref expr_lines), Ok(ref arm_start_lines)) if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col && expr_lines.lines.len() == 2 && self.token == token::FatArrow => { // We check whether there's any trailing code in the parse span, // if there isn't, we very likely have the following: // // X | &Y => "y" // | -- - missing comma // | | // | arrow_span // X | &X => "x" // | - ^^ self.span // | | // | parsed until here as `"y" & X` err.span_suggestion_short( cm.next_point(arm_start_span), "missing a comma here to end this `match` arm", ",".to_owned(), Applicability::MachineApplicable ); } _ => { err.span_label(arrow_span, "while parsing the `match` arm starting here"); } } err })?; } else { self.eat(&token::Comma); } Ok(ast::Arm { attrs, pats, guard, body: expr, }) } /// Parses an expression. #[inline] pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> { self.parse_expr_res(Restrictions::empty(), None) } /// Evaluates the closure with restrictions in place. /// /// Afters the closure is evaluated, restrictions are reset. fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T where F: FnOnce(&mut Self) -> T { let old = self.restrictions; self.restrictions = r; let r = f(self); self.restrictions = old; return r; } /// Parses an expression, subject to the given restrictions. #[inline] fn parse_expr_res(&mut self, r: Restrictions, already_parsed_attrs: Option<ThinVec<Attribute>>) -> PResult<'a, P<Expr>> { self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs)) } /// Parses the RHS of a local variable declaration (e.g., '= 14;'). fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> { if self.eat(&token::Eq) { Ok(Some(self.parse_expr()?)) } else if skip_eq { Ok(Some(self.parse_expr()?)) } else { Ok(None) } } /// Parses patterns, separated by '|' s. fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> { // Allow a '|' before the pats (RFC 1925 + RFC 2530) self.eat(&token::BinOp(token::Or)); let mut pats = Vec::new(); loop { pats.push(self.parse_top_level_pat()?); if self.token == token::OrOr { let mut err = self.struct_span_err(self.span, "unexpected token `||` after pattern"); err.span_suggestion( self.span, "use a single `|` to specify multiple patterns", "|".to_owned(), Applicability::MachineApplicable ); err.emit(); self.bump(); } else if self.eat(&token::BinOp(token::Or)) { // This is a No-op. Continue the loop to parse the next // pattern. } else { return Ok(pats); } }; } // Parses a parenthesized list of patterns like // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns: // - a vector of the patterns that were parsed // - an option indicating the index of the `..` element // - a boolean indicating whether a trailing comma was present. // Trailing commas are significant because (p) and (p,) are different patterns. fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> { self.expect(&token::OpenDelim(token::Paren))?; let result = self.parse_pat_list()?; self.expect(&token::CloseDelim(token::Paren))?; Ok(result) } fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> { let mut fields = Vec::new(); let mut ddpos = None; let mut trailing_comma = false; loop { if self.eat(&token::DotDot) { if ddpos.is_none() { ddpos = Some(fields.len()); } else { // Emit a friendly error, ignore `..` and continue parsing self.struct_span_err( self.prev_span, "`..` can only be used once per tuple or tuple struct pattern", ) .span_label(self.prev_span, "can only be used once per pattern") .emit(); } } else if !self.check(&token::CloseDelim(token::Paren)) { fields.push(self.parse_pat(None)?); } else { break } trailing_comma = self.eat(&token::Comma); if !trailing_comma { break } } if ddpos == Some(fields.len()) && trailing_comma { // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed. let msg = "trailing comma is not permitted after `..`"; self.struct_span_err(self.prev_span, msg) .span_label(self.prev_span, msg) .emit(); } Ok((fields, ddpos, trailing_comma)) } fn parse_pat_vec_elements( &mut self, ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> { let mut before = Vec::new(); let mut slice = None; let mut after = Vec::new(); let mut first = true; let mut before_slice = true; while self.token != token::CloseDelim(token::Bracket) { if first { first = false; } else { self.expect(&token::Comma)?; if self.token == token::CloseDelim(token::Bracket) && (before_slice || !after.is_empty()) { break } } if before_slice { if self.eat(&token::DotDot) { if self.check(&token::Comma) || self.check(&token::CloseDelim(token::Bracket)) { slice = Some(P(Pat { id: ast::DUMMY_NODE_ID, node: PatKind::Wild, span: self.prev_span, })); before_slice = false; } continue } } let subpat = self.parse_pat(None)?; if before_slice && self.eat(&token::DotDot) { slice = Some(subpat); before_slice = false; } else if before_slice { before.push(subpat); } else { after.push(subpat); } } Ok((before, slice, after)) } fn parse_pat_field( &mut self, lo: Span, attrs: Vec<Attribute> ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> { // Check if a colon exists one ahead. This means we're parsing a fieldname. let hi; let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) { // Parsing a pattern of the form "fieldname: pat" let fieldname = self.parse_field_name()?; self.bump(); let pat = self.parse_pat(None)?; hi = pat.span; (pat, fieldname, false) } else { // Parsing a pattern of the form "(box) (ref) (mut) fieldname" let is_box = self.eat_keyword(keywords::Box); let boxed_span = self.span; let is_ref = self.eat_keyword(keywords::Ref); let is_mut = self.eat_keyword(keywords::Mut); let fieldname = self.parse_ident()?; hi = self.prev_span; let bind_type = match (is_ref, is_mut) { (true, true) => BindingMode::ByRef(Mutability::Mutable), (true, false) => BindingMode::ByRef(Mutability::Immutable), (false, true) => BindingMode::ByValue(Mutability::Mutable), (false, false) => BindingMode::ByValue(Mutability::Immutable), }; let fieldpat = P(Pat { id: ast::DUMMY_NODE_ID, node: PatKind::Ident(bind_type, fieldname, None), span: boxed_span.to(hi), }); let subpat = if is_box { P(Pat { id: ast::DUMMY_NODE_ID, node: PatKind::Box(fieldpat), span: lo.to(hi), }) } else { fieldpat }; (subpat, fieldname, true) }; Ok(source_map::Spanned { span: lo.to(hi), node: ast::FieldPat { ident: fieldname, pat: subpat, is_shorthand, attrs: attrs.into(), } }) } /// Parses the fields of a struct-like pattern. fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> { let mut fields = Vec::new(); let mut etc = false; let mut ate_comma = true; let mut delayed_err: Option<DiagnosticBuilder<'a>> = None; let mut etc_span = None; while self.token != token::CloseDelim(token::Brace) { let attrs = self.parse_outer_attributes()?; let lo = self.span; // check that a comma comes after every field if !ate_comma { let err = self.struct_span_err(self.prev_span, "expected `,`"); if let Some(mut delayed) = delayed_err { delayed.emit(); } return Err(err); } ate_comma = false; if self.check(&token::DotDot) || self.token == token::DotDotDot { etc = true; let mut etc_sp = self.span; if self.token == token::DotDotDot { // Issue #46718 // Accept `...` as if it were `..` to avoid further errors let mut err = self.struct_span_err(self.span, "expected field pattern, found `...`"); err.span_suggestion( self.span, "to omit remaining fields, use one fewer `.`", "..".to_owned(), Applicability::MachineApplicable ); err.emit(); } self.bump(); // `..` || `...` if self.token == token::CloseDelim(token::Brace) { etc_span = Some(etc_sp); break; } let token_str = self.this_token_descr(); let mut err = self.fatal(&format!("expected `}}`, found {}", token_str)); err.span_label(self.span, "expected `}`"); let mut comma_sp = None; if self.token == token::Comma { // Issue #49257 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span)); err.span_label(etc_sp, "`..` must be at the end and cannot have a trailing comma"); comma_sp = Some(self.span); self.bump(); ate_comma = true; } etc_span = Some(etc_sp.until(self.span)); if self.token == token::CloseDelim(token::Brace) { // If the struct looks otherwise well formed, recover and continue. if let Some(sp) = comma_sp { err.span_suggestion_short( sp, "remove this comma", String::new(), Applicability::MachineApplicable, ); } err.emit(); break; } else if self.token.is_ident() && ate_comma { // Accept fields coming after `..,`. // This way we avoid "pattern missing fields" errors afterwards. // We delay this error until the end in order to have a span for a // suggested fix. if let Some(mut delayed_err) = delayed_err { delayed_err.emit(); return Err(err); } else { delayed_err = Some(err); } } else { if let Some(mut err) = delayed_err { err.emit(); } return Err(err); } } fields.push(match self.parse_pat_field(lo, attrs) { Ok(field) => field, Err(err) => { if let Some(mut delayed_err) = delayed_err { delayed_err.emit(); } return Err(err); } }); ate_comma = self.eat(&token::Comma); } if let Some(mut err) = delayed_err { if let Some(etc_span) = etc_span { err.multipart_suggestion( "move the `..` to the end of the field list", vec![ (etc_span, String::new()), (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })), ], Applicability::MachineApplicable, ); } err.emit(); } return Ok((fields, etc)); } fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> { if self.token.is_path_start() { let lo = self.span; let (qself, path) = if self.eat_lt() { // Parse a qualified path let (qself, path) = self.parse_qpath(PathStyle::Expr)?; (Some(qself), path) } else { // Parse an unqualified path (None, self.parse_path(PathStyle::Expr)?) }; let hi = self.prev_span; Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new())) } else { self.parse_literal_maybe_minus() } } // helper function to decide whether to parse as ident binding or to try to do // something more complex like range patterns fn parse_as_ident(&mut self) -> bool { self.look_ahead(1, |t| match *t { token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) | token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false), // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the // range pattern branch token::DotDot => None, _ => Some(true), }).unwrap_or_else(|| self.look_ahead(2, |t| match *t { token::Comma | token::CloseDelim(token::Bracket) => true, _ => false, })) } /// A wrapper around `parse_pat` with some special error handling for the /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast /// to subpatterns within such). fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> { let pat = self.parse_pat(None)?; if self.token == token::Comma { // An unexpected comma after a top-level pattern is a clue that the // user (perhaps more accustomed to some other language) forgot the // parentheses in what should have been a tuple pattern; return a // suggestion-enhanced error here rather than choking on the comma // later. let comma_span = self.span; self.bump(); if let Err(mut err) = self.parse_pat_list() { // We didn't expect this to work anyway; we just wanted // to advance to the end of the comma-sequence so we know // the span to suggest parenthesizing err.cancel(); } let seq_span = pat.span.to(self.prev_span); let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern"); if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) { err.span_suggestion( seq_span, "try adding parentheses to match on a tuple..", format!("({})", seq_snippet), Applicability::MachineApplicable ).span_suggestion( seq_span, "..or a vertical bar to match on multiple alternatives", format!("{}", seq_snippet.replace(",", " |")), Applicability::MachineApplicable ); } return Err(err); } Ok(pat) } /// Parses a pattern. pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> { self.parse_pat_with_range_pat(true, expected) } /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are /// allowed). fn parse_pat_with_range_pat( &mut self, allow_range_pat: bool, expected: Option<&'static str>, ) -> PResult<'a, P<Pat>> { maybe_whole!(self, NtPat, |x| x); let lo = self.span; let pat; match self.token { token::BinOp(token::And) | token::AndAnd => { // Parse &pat / &mut pat self.expect_and()?; let mutbl = self.parse_mutability(); if let token::Lifetime(ident) = self.token { let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern", ident)); err.span_label(self.span, "unexpected lifetime"); return Err(err); } let subpat = self.parse_pat_with_range_pat(false, expected)?; pat = PatKind::Ref(subpat, mutbl); } token::OpenDelim(token::Paren) => { // Parse (pat,pat,pat,...) as tuple pattern let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?; pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma { PatKind::Paren(fields.into_iter().nth(0).unwrap()) } else { PatKind::Tuple(fields, ddpos) }; } token::OpenDelim(token::Bracket) => { // Parse [pat,pat,...] as slice pattern self.bump(); let (before, slice, after) = self.parse_pat_vec_elements()?; self.expect(&token::CloseDelim(token::Bracket))?; pat = PatKind::Slice(before, slice, after); } // At this point, token != &, &&, (, [ _ => if self.eat_keyword(keywords::Underscore) { // Parse _ pat = PatKind::Wild; } else if self.eat_keyword(keywords::Mut) { // Parse mut ident @ pat / mut ref ident @ pat let mutref_span = self.prev_span.to(self.span); let binding_mode = if self.eat_keyword(keywords::Ref) { self.diagnostic() .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect") .span_suggestion( mutref_span, "try switching the order", "ref mut".into(), Applicability::MachineApplicable ).emit(); BindingMode::ByRef(Mutability::Mutable) } else { BindingMode::ByValue(Mutability::Mutable) }; pat = self.parse_pat_ident(binding_mode)?; } else if self.eat_keyword(keywords::Ref) { // Parse ref ident @ pat / ref mut ident @ pat let mutbl = self.parse_mutability(); pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?; } else if self.eat_keyword(keywords::Box) { // Parse box pat let subpat = self.parse_pat_with_range_pat(false, None)?; pat = PatKind::Box(subpat); } else if self.token.is_ident() && !self.token.is_reserved_ident() && self.parse_as_ident() { // Parse ident @ pat // This can give false positives and parse nullary enums, // they are dealt with later in resolve let binding_mode = BindingMode::ByValue(Mutability::Immutable); pat = self.parse_pat_ident(binding_mode)?; } else if self.token.is_path_start() { // Parse pattern starting with a path let (qself, path) = if self.eat_lt() { // Parse a qualified path let (qself, path) = self.parse_qpath(PathStyle::Expr)?; (Some(qself), path) } else { // Parse an unqualified path (None, self.parse_path(PathStyle::Expr)?) }; match self.token { token::Not if qself.is_none() => { // Parse macro invocation self.bump(); let (delim, tts) = self.expect_delimited_token_tree()?; let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim }); pat = PatKind::Mac(mac); } token::DotDotDot | token::DotDotEq | token::DotDot => { let end_kind = match self.token { token::DotDot => RangeEnd::Excluded, token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot), token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq), _ => panic!("can only parse `..`/`...`/`..=` for ranges \ (checked above)"), }; let op_span = self.span; // Parse range let span = lo.to(self.prev_span); let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new()); self.bump(); let end = self.parse_pat_range_end()?; let op = Spanned { span: op_span, node: end_kind }; pat = PatKind::Range(begin, end, op); } token::OpenDelim(token::Brace) => { if qself.is_some() { let msg = "unexpected `{` after qualified path"; let mut err = self.fatal(msg); err.span_label(self.span, msg); return Err(err); } // Parse struct pattern self.bump(); let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| { e.emit(); self.recover_stmt(); (vec![], false) }); self.bump(); pat = PatKind::Struct(path, fields, etc); } token::OpenDelim(token::Paren) => { if qself.is_some() { let msg = "unexpected `(` after qualified path"; let mut err = self.fatal(msg); err.span_label(self.span, msg); return Err(err); } // Parse tuple struct or enum pattern let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?; pat = PatKind::TupleStruct(path, fields, ddpos) } _ => pat = PatKind::Path(qself, path), } } else { // Try to parse everything else as literal with optional minus match self.parse_literal_maybe_minus() { Ok(begin) => { let op_span = self.span; if self.check(&token::DotDot) || self.check(&token::DotDotEq) || self.check(&token::DotDotDot) { let end_kind = if self.eat(&token::DotDotDot) { RangeEnd::Included(RangeSyntax::DotDotDot) } else if self.eat(&token::DotDotEq) { RangeEnd::Included(RangeSyntax::DotDotEq) } else if self.eat(&token::DotDot) { RangeEnd::Excluded } else { panic!("impossible case: we already matched \ on a range-operator token") }; let end = self.parse_pat_range_end()?; let op = Spanned { span: op_span, node: end_kind }; pat = PatKind::Range(begin, end, op); } else { pat = PatKind::Lit(begin); } } Err(mut err) => { self.cancel(&mut err); let expected = expected.unwrap_or("pattern"); let msg = format!( "expected {}, found {}", expected, self.this_token_descr(), ); let mut err = self.fatal(&msg); err.span_label(self.span, format!("expected {}", expected)); return Err(err); } } } } let pat = Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID }; let pat = self.maybe_recover_from_bad_qpath(pat, true)?; if !allow_range_pat { match pat.node { PatKind::Range( _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. } ) => {}, PatKind::Range(..) => { let mut err = self.struct_span_err( pat.span, "the range pattern here has ambiguous interpretation", ); err.span_suggestion( pat.span, "add parentheses to clarify the precedence", format!("({})", pprust::pat_to_string(&pat)), // "ambiguous interpretation" implies that we have to be guessing Applicability::MaybeIncorrect ); return Err(err); } _ => {} } } Ok(P(pat)) } /// Parses `ident` or `ident @ pat`. /// used by the copy foo and ref foo patterns to give a good /// error message when parsing mistakes like `ref foo(a, b)`. fn parse_pat_ident(&mut self, binding_mode: ast::BindingMode) -> PResult<'a, PatKind> { let ident = self.parse_ident()?; let sub = if self.eat(&token::At) { Some(self.parse_pat(Some("binding pattern"))?) } else { None }; // just to be friendly, if they write something like // ref Some(i) // we end up here with ( as the current token. This shortly // leads to a parse error. Note that if there is no explicit // binding mode then we do not end up here, because the lookahead // will direct us over to parse_enum_variant() if self.token == token::OpenDelim(token::Paren) { return Err(self.span_fatal( self.prev_span, "expected identifier, found enum pattern")) } Ok(PatKind::Ident(binding_mode, ident, sub)) } /// Parses a local variable declaration. fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> { let lo = self.prev_span; let pat = self.parse_top_level_pat()?; let (err, ty) = if self.eat(&token::Colon) { // Save the state of the parser before parsing type normally, in case there is a `:` // instead of an `=` typo. let parser_snapshot_before_type = self.clone(); let colon_sp = self.prev_span; match self.parse_ty() { Ok(ty) => (None, Some(ty)), Err(mut err) => { // Rewind to before attempting to parse the type and continue parsing let parser_snapshot_after_type = self.clone(); mem::replace(self, parser_snapshot_before_type); let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap(); err.span_label(pat.span, format!("while parsing the type for `{}`", snippet)); (Some((parser_snapshot_after_type, colon_sp, err)), None) } } } else { (None, None) }; let init = match (self.parse_initializer(err.is_some()), err) { (Ok(init), None) => { // init parsed, ty parsed init } (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error // Could parse the type as if it were the initializer, it is likely there was a // typo in the code: `:` instead of `=`. Add suggestion and emit the error. err.span_suggestion_short( colon_sp, "use `=` if you meant to assign", "=".to_string(), Applicability::MachineApplicable ); err.emit(); // As this was parsed successfully, continue as if the code has been fixed for the // rest of the file. It will still fail due to the emitted error, but we avoid // extra noise. init } (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error init_err.cancel(); // Couldn't parse the type nor the initializer, only raise the type error and // return to the parser state before parsing the type as the initializer. // let x: <parse_error>; mem::replace(self, snapshot); return Err(ty_err); } (Err(err), None) => { // init error, ty parsed // Couldn't parse the initializer and we're not attempting to recover a failed // parse of the type, return the error. return Err(err); } }; let hi = if self.token == token::Semi { self.span } else { self.prev_span }; Ok(P(ast::Local { ty, pat, init, id: ast::DUMMY_NODE_ID, span: lo.to(hi), attrs, })) } /// Parses a structure field. fn parse_name_and_ty(&mut self, lo: Span, vis: Visibility, attrs: Vec<Attribute>) -> PResult<'a, StructField> { let name = self.parse_ident()?; self.expect(&token::Colon)?; let ty = self.parse_ty()?; Ok(StructField { span: lo.to(self.prev_span), ident: Some(name), vis, id: ast::DUMMY_NODE_ID, ty, attrs, }) } /// Emits an expected-item-after-attributes error. fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> { let message = match attrs.last() { Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment", _ => "expected item after attributes", }; let mut err = self.diagnostic().struct_span_err(self.prev_span, message); if attrs.last().unwrap().is_sugared_doc { err.span_label(self.prev_span, "this doc comment doesn't document anything"); } Err(err) } /// Parse a statement. This stops just before trailing semicolons on everything but items. /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed. pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> { Ok(self.parse_stmt_(true)) } // Eat tokens until we can be relatively sure we reached the end of the // statement. This is something of a best-effort heuristic. // // We terminate when we find an unmatched `}` (without consuming it). fn recover_stmt(&mut self) { self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore) } // If `break_on_semi` is `Break`, then we will stop consuming tokens after // finding (and consuming) a `;` outside of `{}` or `[]` (note that this is // approximate - it can mean we break too early due to macros, but that // should only lead to sub-optimal recovery, not inaccurate parsing). // // If `break_on_block` is `Break`, then we will stop consuming tokens // after finding (and consuming) a brace-delimited block. fn recover_stmt_(&mut self, break_on_semi: SemiColonMode, break_on_block: BlockMode) { let mut brace_depth = 0; let mut bracket_depth = 0; let mut in_block = false; debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block); loop { debug!("recover_stmt_ loop {:?}", self.token); match self.token { token::OpenDelim(token::DelimToken::Brace) => { brace_depth += 1; self.bump(); if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0 { in_block = true; } } token::OpenDelim(token::DelimToken::Bracket) => { bracket_depth += 1; self.bump(); } token::CloseDelim(token::DelimToken::Brace) => { if brace_depth == 0 { debug!("recover_stmt_ return - close delim {:?}", self.token); break; } brace_depth -= 1; self.bump(); if in_block && bracket_depth == 0 && brace_depth == 0 { debug!("recover_stmt_ return - block end {:?}", self.token); break; } } token::CloseDelim(token::DelimToken::Bracket) => { bracket_depth -= 1; if bracket_depth < 0 { bracket_depth = 0; } self.bump(); } token::Eof => { debug!("recover_stmt_ return - Eof"); break; } token::Semi => { self.bump(); if break_on_semi == SemiColonMode::Break && brace_depth == 0 && bracket_depth == 0 { debug!("recover_stmt_ return - Semi"); break; } } token::Comma => { if break_on_semi == SemiColonMode::Comma && brace_depth == 0 && bracket_depth == 0 { debug!("recover_stmt_ return - Semi"); break; } else { self.bump(); } } _ => { self.bump() } } } } fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> { self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| { e.emit(); self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore); None }) } fn is_async_block(&mut self) -> bool { self.token.is_keyword(keywords::Async) && ( ( // `async move {` self.look_ahead(1, |t| t.is_keyword(keywords::Move)) && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) ) || ( // `async {` self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) ) ) } fn is_do_catch_block(&mut self) -> bool { self.token.is_keyword(keywords::Do) && self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL) } fn is_try_block(&mut self) -> bool { self.token.is_keyword(keywords::Try) && self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) && self.span.rust_2018() && // prevent `while try {} {}`, `if try {} {} else {}`, etc. !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL) } fn is_union_item(&self) -> bool { self.token.is_keyword(keywords::Union) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()) } fn is_crate_vis(&self) -> bool { self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep) } fn is_existential_type_decl(&self) -> bool { self.token.is_keyword(keywords::Existential) && self.look_ahead(1, |t| t.is_keyword(keywords::Type)) } fn is_auto_trait_item(&mut self) -> bool { // auto trait (self.token.is_keyword(keywords::Auto) && self.look_ahead(1, |t| t.is_keyword(keywords::Trait))) || // unsafe auto trait (self.token.is_keyword(keywords::Unsafe) && self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) && self.look_ahead(2, |t| t.is_keyword(keywords::Trait))) } fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span) -> PResult<'a, Option<P<Item>>> { let token_lo = self.span; let (ident, def) = match self.token { token::Ident(ident, false) if ident.name == keywords::Macro.name() => { self.bump(); let ident = self.parse_ident()?; let tokens = if self.check(&token::OpenDelim(token::Brace)) { match self.parse_token_tree() { TokenTree::Delimited(_, _, tts) => tts, _ => unreachable!(), } } else if self.check(&token::OpenDelim(token::Paren)) { let args = self.parse_token_tree(); let body = if self.check(&token::OpenDelim(token::Brace)) { self.parse_token_tree() } else { self.unexpected()?; unreachable!() }; TokenStream::new(vec![ args.into(), TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(), body.into(), ]) } else { self.unexpected()?; unreachable!() }; (ident, ast::MacroDef { tokens: tokens.into(), legacy: false }) } token::Ident(ident, _) if ident.name == "macro_rules" && self.look_ahead(1, |t| *t == token::Not) => { let prev_span = self.prev_span; self.complain_if_pub_macro(&vis.node, prev_span); self.bump(); self.bump(); let ident = self.parse_ident()?; let (delim, tokens) = self.expect_delimited_token_tree()?; if delim != MacDelimiter::Brace { if !self.eat(&token::Semi) { let msg = "macros that expand to items must either \ be surrounded with braces or followed by a semicolon"; self.span_err(self.prev_span, msg); } } (ident, ast::MacroDef { tokens: tokens, legacy: true }) } _ => return Ok(None), }; let span = lo.to(self.prev_span); Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec()))) } fn parse_stmt_without_recovery(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> { maybe_whole!(self, NtStmt, |x| Some(x)); let attrs = self.parse_outer_attributes()?; let lo = self.span; Ok(Some(if self.eat_keyword(keywords::Let) { Stmt { id: ast::DUMMY_NODE_ID, node: StmtKind::Local(self.parse_local(attrs.into())?), span: lo.to(self.prev_span), } } else if let Some(macro_def) = self.eat_macro_def( &attrs, &source_map::respan(lo, VisibilityKind::Inherited), lo, )? { Stmt { id: ast::DUMMY_NODE_ID, node: StmtKind::Item(macro_def), span: lo.to(self.prev_span), } // Starts like a simple path, being careful to avoid contextual keywords // such as a union items, item with `crate` visibility or auto trait items. // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts // like a path (1 token), but it fact not a path. // `union::b::c` - path, `union U { ... }` - not a path. // `crate::b::c` - path, `crate struct S;` - not a path. } else if self.token.is_path_start() && !self.token.is_qpath_start() && !self.is_union_item() && !self.is_crate_vis() && !self.is_existential_type_decl() && !self.is_auto_trait_item() { let pth = self.parse_path(PathStyle::Expr)?; if !self.eat(&token::Not) { let expr = if self.check(&token::OpenDelim(token::Brace)) { self.parse_struct_expr(lo, pth, ThinVec::new())? } else { let hi = self.prev_span; self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new()) }; let expr = self.with_res(Restrictions::STMT_EXPR, |this| { let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?; this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr)) })?; return Ok(Some(Stmt { id: ast::DUMMY_NODE_ID, node: StmtKind::Expr(expr), span: lo.to(self.prev_span), })); } // it's a macro invocation let id = match self.token { token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier _ => self.parse_ident()?, }; // check that we're pointing at delimiters (need to check // again after the `if`, because of `parse_ident` // consuming more tokens). match self.token { token::OpenDelim(_) => {} _ => { // we only expect an ident if we didn't parse one // above. let ident_str = if id.name == keywords::Invalid.name() { "identifier, " } else { "" }; let tok_str = self.this_token_descr(); let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}", ident_str, tok_str)); err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str)); return Err(err) }, } let (delim, tts) = self.expect_delimited_token_tree()?; let hi = self.prev_span; let style = if delim == MacDelimiter::Brace { MacStmtStyle::Braces } else { MacStmtStyle::NoBraces }; if id.name == keywords::Invalid.name() { let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim }); let node = if delim == MacDelimiter::Brace || self.token == token::Semi || self.token == token::Eof { StmtKind::Mac(P((mac, style, attrs.into()))) } // We used to incorrectly stop parsing macro-expanded statements here. // If the next token will be an error anyway but could have parsed with the // earlier behavior, stop parsing here and emit a warning to avoid breakage. else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token { // These can continue an expression, so we can't stop parsing and warn. token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) | token::BinOp(token::Minus) | token::BinOp(token::Star) | token::BinOp(token::And) | token::BinOp(token::Or) | token::AndAnd | token::OrOr | token::DotDot | token::DotDotDot | token::DotDotEq => false, _ => true, } { self.warn_missing_semicolon(); StmtKind::Mac(P((mac, style, attrs.into()))) } else { let e = self.mk_mac_expr(lo.to(hi), mac.node, ThinVec::new()); let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?; let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?; StmtKind::Expr(e) }; Stmt { id: ast::DUMMY_NODE_ID, span: lo.to(hi), node, } } else { // if it has a special ident, it's definitely an item // // Require a semicolon or braces. if style != MacStmtStyle::Braces { if !self.eat(&token::Semi) { self.span_err(self.prev_span, "macros that expand to items must \ either be surrounded with braces or \ followed by a semicolon"); } } let span = lo.to(hi); Stmt { id: ast::DUMMY_NODE_ID, span, node: StmtKind::Item({ self.mk_item( span, id /*id is good here*/, ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })), respan(lo, VisibilityKind::Inherited), attrs) }), } } } else { // FIXME: Bad copy of attrs let old_directory_ownership = mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock); let item = self.parse_item_(attrs.clone(), false, true)?; self.directory.ownership = old_directory_ownership; match item { Some(i) => Stmt { id: ast::DUMMY_NODE_ID, span: lo.to(i.span), node: StmtKind::Item(i), }, None => { let unused_attrs = |attrs: &[Attribute], s: &mut Self| { if !attrs.is_empty() { if s.prev_token_kind == PrevTokenKind::DocComment { s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit(); } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) { s.span_err(s.span, "expected statement after outer attribute"); } } }; // Do not attempt to parse an expression if we're done here. if self.token == token::Semi { unused_attrs(&attrs, self); self.bump(); return Ok(None); } if self.token == token::CloseDelim(token::Brace) { unused_attrs(&attrs, self); return Ok(None); } // Remainder are line-expr stmts. let e = self.parse_expr_res( Restrictions::STMT_EXPR, Some(attrs.into()))?; Stmt { id: ast::DUMMY_NODE_ID, span: lo.to(e.span), node: StmtKind::Expr(e), } } } })) } /// Checks if this expression is a successfully parsed statement. fn expr_is_complete(&mut self, e: &Expr) -> bool { self.restrictions.contains(Restrictions::STMT_EXPR) && !classify::expr_requires_semi_to_be_stmt(e) } /// Parses a block. No inner attributes are allowed. pub fn parse_block(&mut self) -> PResult<'a, P<Block>> { maybe_whole!(self, NtBlock, |x| x); let lo = self.span; if !self.eat(&token::OpenDelim(token::Brace)) { let sp = self.span; let tok = self.this_token_descr(); let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok)); let do_not_suggest_help = self.token.is_keyword(keywords::In) || self.token == token::Colon; if self.token.is_ident_named("and") { e.span_suggestion_short( self.span, "use `&&` instead of `and` for the boolean operator", "&&".to_string(), Applicability::MaybeIncorrect, ); } if self.token.is_ident_named("or") { e.span_suggestion_short( self.span, "use `||` instead of `or` for the boolean operator", "||".to_string(), Applicability::MaybeIncorrect, ); } // Check to see if the user has written something like // // if (cond) // bar; // // Which is valid in other languages, but not Rust. match self.parse_stmt_without_recovery(false) { Ok(Some(stmt)) => { if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace)) || do_not_suggest_help { // if the next token is an open brace (e.g., `if a b {`), the place- // inside-a-block suggestion would be more likely wrong than right e.span_label(sp, "expected `{`"); return Err(e); } let mut stmt_span = stmt.span; // expand the span to include the semicolon, if it exists if self.eat(&token::Semi) { stmt_span = stmt_span.with_hi(self.prev_span.hi()); } let sugg = pprust::to_string(|s| { use crate::print::pprust::{PrintState, INDENT_UNIT}; s.ibox(INDENT_UNIT)?; s.bopen()?; s.print_stmt(&stmt)?; s.bclose_maybe_open(stmt.span, INDENT_UNIT, false) }); e.span_suggestion( stmt_span, "try placing this code inside a block", sugg, // speculative, has been misleading in the past (closed Issue #46836) Applicability::MaybeIncorrect ); } Err(mut e) => { self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore); self.cancel(&mut e); } _ => () } e.span_label(sp, "expected `{`"); return Err(e); } self.parse_block_tail(lo, BlockCheckMode::Default) } /// Parses a block. Inner attributes are allowed. fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> { maybe_whole!(self, NtBlock, |x| (Vec::new(), x)); let lo = self.span; self.expect(&token::OpenDelim(token::Brace))?; Ok((self.parse_inner_attributes()?, self.parse_block_tail(lo, BlockCheckMode::Default)?)) } /// Parses the rest of a block expression or function body. /// Precondition: already parsed the '{'. fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> { let mut stmts = vec![]; while !self.eat(&token::CloseDelim(token::Brace)) { let stmt = match self.parse_full_stmt(false) { Err(mut err) => { err.emit(); self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore); Some(Stmt { id: ast::DUMMY_NODE_ID, node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)), span: self.span, }) } Ok(stmt) => stmt, }; if let Some(stmt) = stmt { stmts.push(stmt); } else if self.token == token::Eof { break; } else { // Found only `;` or `}`. continue; }; } Ok(P(ast::Block { stmts, id: ast::DUMMY_NODE_ID, rules: s, span: lo.to(self.prev_span), })) } /// Parses a statement, including the trailing semicolon. crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> { // skip looking for a trailing semicolon when we have an interpolated statement maybe_whole!(self, NtStmt, |x| Some(x)); let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? { Some(stmt) => stmt, None => return Ok(None), }; match stmt.node { StmtKind::Expr(ref expr) if self.token != token::Eof => { // expression without semicolon if classify::expr_requires_semi_to_be_stmt(expr) { // Just check for errors and recover; do not eat semicolon yet. if let Err(mut e) = self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)]) { e.emit(); self.recover_stmt(); } } } StmtKind::Local(..) => { // We used to incorrectly allow a macro-expanded let statement to lack a semicolon. if macro_legacy_warnings && self.token != token::Semi { self.warn_missing_semicolon(); } else { self.expect_one_of(&[], &[token::Semi])?; } } _ => {} } if self.eat(&token::Semi) { stmt = stmt.add_trailing_semicolon(); } stmt.span = stmt.span.with_hi(self.prev_span.hi()); Ok(Some(stmt)) } fn warn_missing_semicolon(&self) { self.diagnostic().struct_span_warn(self.span, { &format!("expected `;`, found {}", self.this_token_descr()) }).note({ "This was erroneously allowed and will become a hard error in a future release" }).emit(); } fn err_dotdotdot_syntax(&self, span: Span) { self.diagnostic().struct_span_err(span, { "unexpected token: `...`" }).span_suggestion( span, "use `..` for an exclusive range", "..".to_owned(), Applicability::MaybeIncorrect ).span_suggestion( span, "or `..=` for an inclusive range", "..=".to_owned(), Applicability::MaybeIncorrect ).emit(); } /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`. /// /// ``` /// BOUND = TY_BOUND | LT_BOUND /// LT_BOUND = LIFETIME (e.g., `'a`) /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN) /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`) /// ``` fn parse_generic_bounds_common(&mut self, allow_plus: bool, colon_span: Option<Span>) -> PResult<'a, GenericBounds> { let mut bounds = Vec::new(); let mut negative_bounds = Vec::new(); let mut last_plus_span = None; loop { // This needs to be synchronized with `Token::can_begin_bound`. let is_bound_start = self.check_path() || self.check_lifetime() || self.check(&token::Not) || // used for error reporting only self.check(&token::Question) || self.check_keyword(keywords::For) || self.check(&token::OpenDelim(token::Paren)); if is_bound_start { let lo = self.span; let has_parens = self.eat(&token::OpenDelim(token::Paren)); let inner_lo = self.span; let is_negative = self.eat(&token::Not); let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None }; if self.token.is_lifetime() { if let Some(question_span) = question { self.span_err(question_span, "`?` may only modify trait bounds, not lifetime bounds"); } bounds.push(GenericBound::Outlives(self.expect_lifetime())); if has_parens { let inner_span = inner_lo.to(self.prev_span); self.expect(&token::CloseDelim(token::Paren))?; let mut err = self.struct_span_err( lo.to(self.prev_span), "parenthesized lifetime bounds are not supported" ); if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) { err.span_suggestion_short( lo.to(self.prev_span), "remove the parentheses", snippet.to_owned(), Applicability::MachineApplicable ); } err.emit(); } } else { let lifetime_defs = self.parse_late_bound_lifetime_defs()?; let path = self.parse_path(PathStyle::Type)?; if has_parens { self.expect(&token::CloseDelim(token::Paren))?; } let poly_span = lo.to(self.prev_span); if is_negative { negative_bounds.push( last_plus_span.or(colon_span).unwrap() .to(poly_span)); } else { let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span); let modifier = if question.is_some() { TraitBoundModifier::Maybe } else { TraitBoundModifier::None }; bounds.push(GenericBound::Trait(poly_trait, modifier)); } } } else { break } if !allow_plus || !self.eat_plus() { break } else { last_plus_span = Some(self.prev_span); } } if !negative_bounds.is_empty() { let plural = negative_bounds.len() > 1; let mut err = self.struct_span_err(negative_bounds, "negative trait bounds are not supported"); let bound_list = colon_span.unwrap().to(self.prev_span); let mut new_bound_list = String::new(); if !bounds.is_empty() { let mut snippets = bounds.iter().map(|bound| bound.span()) .map(|span| self.sess.source_map().span_to_snippet(span)); while let Some(Ok(snippet)) = snippets.next() { new_bound_list.push_str(" + "); new_bound_list.push_str(&snippet); } new_bound_list = new_bound_list.replacen(" +", ":", 1); } err.span_suggestion_short(bound_list, &format!("remove the trait bound{}", if plural { "s" } else { "" }), new_bound_list, Applicability::MachineApplicable); err.emit(); } return Ok(bounds); } fn parse_generic_bounds(&mut self, colon_span: Option<Span>) -> PResult<'a, GenericBounds> { self.parse_generic_bounds_common(true, colon_span) } /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`. /// /// ``` /// BOUND = LT_BOUND (e.g., `'a`) /// ``` fn parse_lt_param_bounds(&mut self) -> GenericBounds { let mut lifetimes = Vec::new(); while self.check_lifetime() { lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime())); if !self.eat_plus() { break } } lifetimes } /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`. fn parse_ty_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> { let ident = self.parse_ident()?; // Parse optional colon and param bounds. let bounds = if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() }; let default = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None }; Ok(GenericParam { ident, id: ast::DUMMY_NODE_ID, attrs: preceding_attrs.into(), bounds, kind: GenericParamKind::Type { default, } }) } /// Parses the following grammar: /// /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty] fn parse_trait_item_assoc_ty(&mut self) -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> { let ident = self.parse_ident()?; let mut generics = self.parse_generics()?; // Parse optional colon and param bounds. let bounds = if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() }; generics.where_clause = self.parse_where_clause()?; let default = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None }; self.expect(&token::Semi)?; Ok((ident, TraitItemKind::Type(bounds, default), generics)) } fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> { self.expect_keyword(keywords::Const)?; let ident = self.parse_ident()?; self.expect(&token::Colon)?; let ty = self.parse_ty()?; Ok(GenericParam { ident, id: ast::DUMMY_NODE_ID, attrs: preceding_attrs.into(), bounds: Vec::new(), kind: GenericParamKind::Const { ty, } }) } /// Parses a (possibly empty) list of lifetime and type parameters, possibly including /// a trailing comma and erroneous trailing attributes. crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> { let mut params = Vec::new(); loop { let attrs = self.parse_outer_attributes()?; if self.check_lifetime() { let lifetime = self.expect_lifetime(); // Parse lifetime parameter. let bounds = if self.eat(&token::Colon) { self.parse_lt_param_bounds() } else { Vec::new() }; params.push(ast::GenericParam { ident: lifetime.ident, id: lifetime.id, attrs: attrs.into(), bounds, kind: ast::GenericParamKind::Lifetime, }); } else if self.check_keyword(keywords::Const) { // Parse const parameter. params.push(self.parse_const_param(attrs)?); } else if self.check_ident() { // Parse type parameter. params.push(self.parse_ty_param(attrs)?); } else { // Check for trailing attributes and stop parsing. if !attrs.is_empty() { if !params.is_empty() { self.struct_span_err( attrs[0].span, &format!("trailing attribute after generic parameter"), ) .span_label(attrs[0].span, "attributes must go before parameters") .emit(); } else { self.struct_span_err( attrs[0].span, &format!("attribute without generic parameters"), ) .span_label( attrs[0].span, "attributes are only permitted when preceding parameters", ) .emit(); } } break } if !self.eat(&token::Comma) { break } } Ok(params) } /// Parses a set of optional generic type parameter declarations. Where /// clauses are not parsed here, and must be added later via /// `parse_where_clause()`. /// /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > ) /// | ( < lifetimes , typaramseq ( , )? > ) /// where typaramseq = ( typaram ) | ( typaram , typaramseq ) fn parse_generics(&mut self) -> PResult<'a, ast::Generics> { maybe_whole!(self, NtGenerics, |x| x); let span_lo = self.span; if self.eat_lt() { let params = self.parse_generic_params()?; self.expect_gt()?; Ok(ast::Generics { params, where_clause: WhereClause { id: ast::DUMMY_NODE_ID, predicates: Vec::new(), span: syntax_pos::DUMMY_SP, }, span: span_lo.to(self.prev_span), }) } else { Ok(ast::Generics::default()) } } /// Parses generic args (within a path segment) with recovery for extra leading angle brackets. /// For the purposes of understanding the parsing logic of generic arguments, this function /// can be thought of being the same as just calling `self.parse_generic_args()` if the source /// had the correct amount of leading angle brackets. /// /// ```ignore (diagnostics) /// bar::<<<<T as Foo>::Output>(); /// ^^ help: remove extra angle brackets /// ``` fn parse_generic_args_with_leaning_angle_bracket_recovery( &mut self, style: PathStyle, lo: Span, ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> { // We need to detect whether there are extra leading left angle brackets and produce an // appropriate error and suggestion. This cannot be implemented by looking ahead at // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens // then there won't be matching `>` tokens to find. // // To explain how this detection works, consider the following example: // // ```ignore (diagnostics) // bar::<<<<T as Foo>::Output>(); // ^^ help: remove extra angle brackets // ``` // // Parsing of the left angle brackets starts in this function. We start by parsing the // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via // `eat_lt`): // // *Upcoming tokens:* `<<<<T as Foo>::Output>;` // *Unmatched count:* 1 // *`parse_path_segment` calls deep:* 0 // // This has the effect of recursing as this function is called if a `<` character // is found within the expected generic arguments: // // *Upcoming tokens:* `<<<T as Foo>::Output>;` // *Unmatched count:* 2 // *`parse_path_segment` calls deep:* 1 // // Eventually we will have recursed until having consumed all of the `<` tokens and // this will be reflected in the count: // // *Upcoming tokens:* `T as Foo>::Output>;` // *Unmatched count:* 4 // `parse_path_segment` calls deep:* 3 // // The parser will continue until reaching the first `>` - this will decrement the // unmatched angle bracket count and return to the parent invocation of this function // having succeeded in parsing: // // *Upcoming tokens:* `::Output>;` // *Unmatched count:* 3 // *`parse_path_segment` calls deep:* 2 // // This will continue until the next `>` character which will also return successfully // to the parent invocation of this function and decrement the count: // // *Upcoming tokens:* `;` // *Unmatched count:* 2 // *`parse_path_segment` calls deep:* 1 // // At this point, this function will expect to find another matching `>` character but // won't be able to and will return an error. This will continue all the way up the // call stack until the first invocation: // // *Upcoming tokens:* `;` // *Unmatched count:* 2 // *`parse_path_segment` calls deep:* 0 // // In doing this, we have managed to work out how many unmatched leading left angle // brackets there are, but we cannot recover as the unmatched angle brackets have // already been consumed. To remedy this, we keep a snapshot of the parser state // before we do the above. We can then inspect whether we ended up with a parsing error // and unmatched left angle brackets and if so, restore the parser state before we // consumed any `<` characters to emit an error and consume the erroneous tokens to // recover by attempting to parse again. // // In practice, the recursion of this function is indirect and there will be other // locations that consume some `<` characters - as long as we update the count when // this happens, it isn't an issue. let is_first_invocation = style == PathStyle::Expr; // Take a snapshot before attempting to parse - we can restore this later. let snapshot = if is_first_invocation { Some(self.clone()) } else { None }; debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)"); match self.parse_generic_args() { Ok(value) => Ok(value), Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => { // Cancel error from being unable to find `>`. We know the error // must have been this due to a non-zero unmatched angle bracket // count. e.cancel(); // Swap `self` with our backup of the parser state before attempting to parse // generic arguments. let snapshot = mem::replace(self, snapshot.unwrap()); debug!( "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \ snapshot.count={:?}", snapshot.unmatched_angle_bracket_count, ); // Eat the unmatched angle brackets. for _ in 0..snapshot.unmatched_angle_bracket_count { self.eat_lt(); } // Make a span over ${unmatched angle bracket count} characters. let span = lo.with_hi( lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count) ); let plural = snapshot.unmatched_angle_bracket_count > 1; self.diagnostic() .struct_span_err( span, &format!( "unmatched angle bracket{}", if plural { "s" } else { "" } ), ) .span_suggestion( span, &format!( "remove extra angle bracket{}", if plural { "s" } else { "" } ), String::new(), Applicability::MachineApplicable, ) .emit(); // Try again without unmatched angle bracket characters. self.parse_generic_args() }, Err(e) => Err(e), } } /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings, /// possibly including trailing comma. fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> { let mut args = Vec::new(); let mut bindings = Vec::new(); let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new(); let mut assoc_ty_bindings: Vec<Span> = Vec::new(); let args_lo = self.span; loop { if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) { // Parse lifetime argument. args.push(GenericArg::Lifetime(self.expect_lifetime())); misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings); } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) { // Parse associated type binding. let lo = self.span; let ident = self.parse_ident()?; self.bump(); let ty = self.parse_ty()?; let span = lo.to(self.prev_span); bindings.push(TypeBinding { id: ast::DUMMY_NODE_ID, ident, ty, span, }); assoc_ty_bindings.push(span); } else if self.check_const_arg() { // FIXME(const_generics): to distinguish between idents for types and consts, // we should introduce a GenericArg::Ident in the AST and distinguish when // lowering to the HIR. For now, idents for const args are not permitted. // Parse const argument. let expr = if let token::OpenDelim(token::Brace) = self.token { self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())? } else if self.token.is_ident() { // FIXME(const_generics): to distinguish between idents for types and consts, // we should introduce a GenericArg::Ident in the AST and distinguish when // lowering to the HIR. For now, idents for const args are not permitted. return Err( self.fatal("identifiers may currently not be used for const generics") ); } else { // FIXME(const_generics): this currently conflicts with emplacement syntax // with negative integer literals. self.parse_literal_maybe_minus()? }; let value = AnonConst { id: ast::DUMMY_NODE_ID, value: expr, }; args.push(GenericArg::Const(value)); misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings); } else if self.check_type() { // Parse type argument. args.push(GenericArg::Type(self.parse_ty()?)); misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings); } else { break } if !self.eat(&token::Comma) { break } } // FIXME: we would like to report this in ast_validation instead, but we currently do not // preserve ordering of generic parameters with respect to associated type binding, so we // lose that information after parsing. if misplaced_assoc_ty_bindings.len() > 0 { let mut err = self.struct_span_err( args_lo.to(self.prev_span), "associated type bindings must be declared after generic parameters", ); for span in misplaced_assoc_ty_bindings { err.span_label( span, "this associated type binding should be moved after the generic parameters", ); } err.emit(); } Ok((args, bindings)) } /// Parses an optional where-clause and places it in `generics`. /// /// ```ignore (only-for-syntax-highlight) /// where T : Trait<U, V> + 'b, 'a : 'b /// ``` fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> { maybe_whole!(self, NtWhereClause, |x| x); let mut where_clause = WhereClause { id: ast::DUMMY_NODE_ID, predicates: Vec::new(), span: syntax_pos::DUMMY_SP, }; if !self.eat_keyword(keywords::Where) { return Ok(where_clause); } let lo = self.prev_span; // We are considering adding generics to the `where` keyword as an alternative higher-rank // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking // change we parse those generics now, but report an error. if self.choose_generics_over_qpath() { let generics = self.parse_generics()?; self.struct_span_err( generics.span, "generic parameters on `where` clauses are reserved for future use", ) .span_label(generics.span, "currently unsupported") .emit(); } loop { let lo = self.span; if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) { let lifetime = self.expect_lifetime(); // Bounds starting with a colon are mandatory, but possibly empty. self.expect(&token::Colon)?; let bounds = self.parse_lt_param_bounds(); where_clause.predicates.push(ast::WherePredicate::RegionPredicate( ast::WhereRegionPredicate { span: lo.to(self.prev_span), lifetime, bounds, } )); } else if self.check_type() { // Parse optional `for<'a, 'b>`. // This `for` is parsed greedily and applies to the whole predicate, // the bounded type can have its own `for` applying only to it. // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/> // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/> // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/> let lifetime_defs = self.parse_late_bound_lifetime_defs()?; // Parse type with mandatory colon and (possibly empty) bounds, // or with mandatory equality sign and the second type. let ty = self.parse_ty()?; if self.eat(&token::Colon) { let bounds = self.parse_generic_bounds(None)?; where_clause.predicates.push(ast::WherePredicate::BoundPredicate( ast::WhereBoundPredicate { span: lo.to(self.prev_span), bound_generic_params: lifetime_defs, bounded_ty: ty, bounds, } )); // FIXME: Decide what should be used here, `=` or `==`. // FIXME: We are just dropping the binders in lifetime_defs on the floor here. } else if self.eat(&token::Eq) || self.eat(&token::EqEq) { let rhs_ty = self.parse_ty()?; where_clause.predicates.push(ast::WherePredicate::EqPredicate( ast::WhereEqPredicate { span: lo.to(self.prev_span), lhs_ty: ty, rhs_ty, id: ast::DUMMY_NODE_ID, } )); } else { return self.unexpected(); } } else { break } if !self.eat(&token::Comma) { break } } where_clause.span = lo.to(self.prev_span); Ok(where_clause) } fn parse_fn_args(&mut self, named_args: bool, allow_variadic: bool) -> PResult<'a, (Vec<Arg> , bool)> { self.expect(&token::OpenDelim(token::Paren))?; let sp = self.span; let mut variadic = false; let (args, recovered): (Vec<Option<Arg>>, bool) = self.parse_seq_to_before_end( &token::CloseDelim(token::Paren), SeqSep::trailing_allowed(token::Comma), |p| { if p.token == token::DotDotDot { p.bump(); variadic = true; if allow_variadic { if p.token != token::CloseDelim(token::Paren) { let span = p.span; p.span_err(span, "`...` must be last in argument list for variadic function"); } Ok(None) } else { let span = p.prev_span; if p.token == token::CloseDelim(token::Paren) { // continue parsing to present any further errors p.struct_span_err( span, "only foreign functions are allowed to be variadic" ).emit(); Ok(Some(dummy_arg(span))) } else { // this function definition looks beyond recovery, stop parsing p.span_err(span, "only foreign functions are allowed to be variadic"); Ok(None) } } } else { match p.parse_arg_general(named_args, false) { Ok(arg) => Ok(Some(arg)), Err(mut e) => { e.emit(); let lo = p.prev_span; // Skip every token until next possible arg or end. p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]); // Create a placeholder argument for proper arg count (#34264). let span = lo.to(p.prev_span); Ok(Some(dummy_arg(span))) } } } } )?; if !recovered { self.eat(&token::CloseDelim(token::Paren)); } let args: Vec<_> = args.into_iter().filter_map(|x| x).collect(); if variadic && args.is_empty() { self.span_err(sp, "variadic function must be declared with at least one named argument"); } Ok((args, variadic)) } /// Parses the argument list and result type of a function declaration. fn parse_fn_decl(&mut self, allow_variadic: bool) -> PResult<'a, P<FnDecl>> { let (args, variadic) = self.parse_fn_args(true, allow_variadic)?; let ret_ty = self.parse_ret_ty(true)?; Ok(P(FnDecl { inputs: args, output: ret_ty, variadic, })) } /// Returns the parsed optional self argument and whether a self shortcut was used. fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> { let expect_ident = |this: &mut Self| match this.token { // Preserve hygienic context. token::Ident(ident, _) => { let span = this.span; this.bump(); Ident::new(ident.name, span) } _ => unreachable!() }; let isolated_self = |this: &mut Self, n| { this.look_ahead(n, |t| t.is_keyword(keywords::SelfLower)) && this.look_ahead(n + 1, |t| t != &token::ModSep) }; // Parse optional self parameter of a method. // Only a limited set of initial token sequences is considered self parameters, anything // else is parsed as a normal function parameter list, so some lookahead is required. let eself_lo = self.span; let (eself, eself_ident, eself_hi) = match self.token { token::BinOp(token::And) => { // &self // &mut self // &'lt self // &'lt mut self // ¬_self (if isolated_self(self, 1) { self.bump(); SelfKind::Region(None, Mutability::Immutable) } else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) && isolated_self(self, 2) { self.bump(); self.bump(); SelfKind::Region(None, Mutability::Mutable) } else if self.look_ahead(1, |t| t.is_lifetime()) && isolated_self(self, 2) { self.bump(); let lt = self.expect_lifetime(); SelfKind::Region(Some(lt), Mutability::Immutable) } else if self.look_ahead(1, |t| t.is_lifetime()) && self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) && isolated_self(self, 3) { self.bump(); let lt = self.expect_lifetime(); self.bump(); SelfKind::Region(Some(lt), Mutability::Mutable) } else { return Ok(None); }, expect_ident(self), self.prev_span) } token::BinOp(token::Star) => { // *self // *const self // *mut self // *not_self // Emit special error for `self` cases. let msg = "cannot pass `self` by raw pointer"; (if isolated_self(self, 1) { self.bump(); self.struct_span_err(self.span, msg) .span_label(self.span, msg) .emit(); SelfKind::Value(Mutability::Immutable) } else if self.look_ahead(1, |t| t.is_mutability()) && isolated_self(self, 2) { self.bump(); self.bump(); self.struct_span_err(self.span, msg) .span_label(self.span, msg) .emit(); SelfKind::Value(Mutability::Immutable) } else { return Ok(None); }, expect_ident(self), self.prev_span) } token::Ident(..) => { if isolated_self(self, 0) { // self // self: TYPE let eself_ident = expect_ident(self); let eself_hi = self.prev_span; (if self.eat(&token::Colon) { let ty = self.parse_ty()?; SelfKind::Explicit(ty, Mutability::Immutable) } else { SelfKind::Value(Mutability::Immutable) }, eself_ident, eself_hi) } else if self.token.is_keyword(keywords::Mut) && isolated_self(self, 1) { // mut self // mut self: TYPE self.bump(); let eself_ident = expect_ident(self); let eself_hi = self.prev_span; (if self.eat(&token::Colon) { let ty = self.parse_ty()?; SelfKind::Explicit(ty, Mutability::Mutable) } else { SelfKind::Value(Mutability::Mutable) }, eself_ident, eself_hi) } else { return Ok(None); } } _ => return Ok(None), }; let eself = source_map::respan(eself_lo.to(eself_hi), eself); Ok(Some(Arg::from_self(eself, eself_ident))) } /// Parses the parameter list and result type of a function that may have a `self` parameter. fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>> where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>, { self.expect(&token::OpenDelim(token::Paren))?; // Parse optional self argument let self_arg = self.parse_self_arg()?; // Parse the rest of the function parameter list. let sep = SeqSep::trailing_allowed(token::Comma); let (fn_inputs, recovered) = if let Some(self_arg) = self_arg { if self.check(&token::CloseDelim(token::Paren)) { (vec![self_arg], false) } else if self.eat(&token::Comma) { let mut fn_inputs = vec![self_arg]; let (mut input, recovered) = self.parse_seq_to_before_end( &token::CloseDelim(token::Paren), sep, parse_arg_fn)?; fn_inputs.append(&mut input); (fn_inputs, recovered) } else { return self.unexpected(); } } else { self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)? }; if !recovered { // Parse closing paren and return type. self.expect(&token::CloseDelim(token::Paren))?; } Ok(P(FnDecl { inputs: fn_inputs, output: self.parse_ret_ty(true)?, variadic: false })) } /// Parses the `|arg, arg|` header of a closure. fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> { let inputs_captures = { if self.eat(&token::OrOr) { Vec::new() } else { self.expect(&token::BinOp(token::Or))?; let args = self.parse_seq_to_before_tokens( &[&token::BinOp(token::Or), &token::OrOr], SeqSep::trailing_allowed(token::Comma), TokenExpectType::NoExpect, |p| p.parse_fn_block_arg() )?.0; self.expect_or()?; args } }; let output = self.parse_ret_ty(true)?; Ok(P(FnDecl { inputs: inputs_captures, output, variadic: false })) } /// Parses the name and optional generic types of a function header. fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> { let id = self.parse_ident()?; let generics = self.parse_generics()?; Ok((id, generics)) } fn mk_item(&mut self, span: Span, ident: Ident, node: ItemKind, vis: Visibility, attrs: Vec<Attribute>) -> P<Item> { P(Item { ident, attrs, id: ast::DUMMY_NODE_ID, node, vis, span, tokens: None, }) } /// Parses an item-position function declaration. fn parse_item_fn(&mut self, unsafety: Unsafety, asyncness: IsAsync, constness: Spanned<Constness>, abi: Abi) -> PResult<'a, ItemInfo> { let (ident, mut generics) = self.parse_fn_header()?; let decl = self.parse_fn_decl(false)?; generics.where_clause = self.parse_where_clause()?; let (inner_attrs, body) = self.parse_inner_attrs_and_block()?; let header = FnHeader { unsafety, asyncness, constness, abi }; Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs))) } /// Returns `true` if we are looking at `const ID` /// (returns `false` for things like `const fn`, etc.). fn is_const_item(&mut self) -> bool { self.token.is_keyword(keywords::Const) && !self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) && !self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) } /// Parses all the "front matter" for a `fn` declaration, up to /// and including the `fn` keyword: /// /// - `const fn` /// - `unsafe fn` /// - `const unsafe fn` /// - `extern fn` /// - etc. fn parse_fn_front_matter(&mut self) -> PResult<'a, ( Spanned<Constness>, Unsafety, IsAsync, Abi )> { let is_const_fn = self.eat_keyword(keywords::Const); let const_span = self.prev_span; let unsafety = self.parse_unsafety(); let asyncness = self.parse_asyncness(); let (constness, unsafety, abi) = if is_const_fn { (respan(const_span, Constness::Const), unsafety, Abi::Rust) } else { let abi = if self.eat_keyword(keywords::Extern) { self.parse_opt_abi()?.unwrap_or(Abi::C) } else { Abi::Rust }; (respan(self.prev_span, Constness::NotConst), unsafety, abi) }; self.expect_keyword(keywords::Fn)?; Ok((constness, unsafety, asyncness, abi)) } /// Parses an impl item. pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> { maybe_whole!(self, NtImplItem, |x| x); let attrs = self.parse_outer_attributes()?; let (mut item, tokens) = self.collect_tokens(|this| { this.parse_impl_item_(at_end, attrs) })?; // See `parse_item` for why this clause is here. if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) { item.tokens = Some(tokens); } Ok(item) } fn parse_impl_item_(&mut self, at_end: &mut bool, mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> { let lo = self.span; let vis = self.parse_visibility(false)?; let defaultness = self.parse_defaultness(); let (name, node, generics) = if let Some(type_) = self.eat_type() { let (name, alias, generics) = type_?; let kind = match alias { AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ), AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds), }; (name, kind, generics) } else if self.is_const_item() { // This parses the grammar: // ImplItemConst = "const" Ident ":" Ty "=" Expr ";" self.expect_keyword(keywords::Const)?; let name = self.parse_ident()?; self.expect(&token::Colon)?; let typ = self.parse_ty()?; self.expect(&token::Eq)?; let expr = self.parse_expr()?; self.expect(&token::Semi)?; (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default()) } else { let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?; attrs.extend(inner_attrs); (name, node, generics) }; Ok(ImplItem { id: ast::DUMMY_NODE_ID, span: lo.to(self.prev_span), ident: name, vis, defaultness, attrs, generics, node, tokens: None, }) } fn complain_if_pub_macro(&mut self, vis: &VisibilityKind, sp: Span) { match *vis { VisibilityKind::Inherited => {} _ => { let is_macro_rules: bool = match self.token { token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"), _ => false, }; let mut err = if is_macro_rules { let mut err = self.diagnostic() .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`"); err.span_suggestion( sp, "try exporting the macro", "#[macro_export]".to_owned(), Applicability::MaybeIncorrect // speculative ); err } else { let mut err = self.diagnostic() .struct_span_err(sp, "can't qualify macro invocation with `pub`"); err.help("try adjusting the macro to put `pub` inside the invocation"); err }; err.emit(); } } } fn missing_assoc_item_kind_err(&mut self, item_type: &str, prev_span: Span) -> DiagnosticBuilder<'a> { let expected_kinds = if item_type == "extern" { "missing `fn`, `type`, or `static`" } else { "missing `fn`, `type`, or `const`" }; // Given this code `path(`, it seems like this is not // setting the visibility of a macro invocation, but rather // a mistyped method declaration. // Create a diagnostic pointing out that `fn` is missing. // // x | pub path(&self) { // | ^ missing `fn`, `type`, or `const` // pub path( // ^^ `sp` below will point to this let sp = prev_span.between(self.prev_span); let mut err = self.diagnostic().struct_span_err( sp, &format!("{} for {}-item declaration", expected_kinds, item_type)); err.span_label(sp, expected_kinds); err } /// Parse a method or a macro invocation in a trait impl. fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool) -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics, ast::ImplItemKind)> { // code copied from parse_macro_use_or_failure... abstraction! if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? { // method macro Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(), ast::ImplItemKind::Macro(mac))) } else { let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?; let ident = self.parse_ident()?; let mut generics = self.parse_generics()?; let decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?; generics.where_clause = self.parse_where_clause()?; *at_end = true; let (inner_attrs, body) = self.parse_inner_attrs_and_block()?; let header = ast::FnHeader { abi, unsafety, constness, asyncness }; Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method( ast::MethodSig { header, decl }, body ))) } } /// Parses `trait Foo { ... }` or `trait Foo = Bar;`. fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> { let ident = self.parse_ident()?; let mut tps = self.parse_generics()?; // Parse optional colon and supertrait bounds. let bounds = if self.eat(&token::Colon) { self.parse_generic_bounds(Some(self.prev_span))? } else { Vec::new() }; if self.eat(&token::Eq) { // it's a trait alias let bounds = self.parse_generic_bounds(None)?; tps.where_clause = self.parse_where_clause()?; self.expect(&token::Semi)?; if is_auto == IsAuto::Yes { let msg = "trait aliases cannot be `auto`"; self.struct_span_err(self.prev_span, msg) .span_label(self.prev_span, msg) .emit(); } if unsafety != Unsafety::Normal { let msg = "trait aliases cannot be `unsafe`"; self.struct_span_err(self.prev_span, msg) .span_label(self.prev_span, msg) .emit(); } Ok((ident, ItemKind::TraitAlias(tps, bounds), None)) } else { // it's a normal trait tps.where_clause = self.parse_where_clause()?; self.expect(&token::OpenDelim(token::Brace))?; let mut trait_items = vec![]; while !self.eat(&token::CloseDelim(token::Brace)) { let mut at_end = false; match self.parse_trait_item(&mut at_end) { Ok(item) => trait_items.push(item), Err(mut e) => { e.emit(); if !at_end { self.recover_stmt_(SemiColonMode::Break, BlockMode::Break); } } } } Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None)) } } fn choose_generics_over_qpath(&self) -> bool { // There's an ambiguity between generic parameters and qualified paths in impls. // If we see `<` it may start both, so we have to inspect some following tokens. // The following combinations can only start generics, // but not qualified paths (with one exception): // `<` `>` - empty generic parameters // `<` `#` - generic parameters with attributes // `<` (LIFETIME|IDENT) `>` - single generic parameter // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds // `<` (LIFETIME|IDENT) `=` - generic parameter with a default // `<` const - generic const parameter // The only truly ambiguous case is // `<` IDENT `>` `::` IDENT ... // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`) // because this is what almost always expected in practice, qualified paths in impls // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment. self.token == token::Lt && (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) || self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) && self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma || t == &token::Colon || t == &token::Eq) || self.look_ahead(1, |t| t.is_keyword(keywords::Const))) } fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> { self.expect(&token::OpenDelim(token::Brace))?; let attrs = self.parse_inner_attributes()?; let mut impl_items = Vec::new(); while !self.eat(&token::CloseDelim(token::Brace)) { let mut at_end = false; match self.parse_impl_item(&mut at_end) { Ok(impl_item) => impl_items.push(impl_item), Err(mut err) => { err.emit(); if !at_end { self.recover_stmt_(SemiColonMode::Break, BlockMode::Break); } } } } Ok((impl_items, attrs)) } /// Parses an implementation item, `impl` keyword is already parsed. /// /// impl<'a, T> TYPE { /* impl items */ } /// impl<'a, T> TRAIT for TYPE { /* impl items */ } /// impl<'a, T> !TRAIT for TYPE { /* impl items */ } /// /// We actually parse slightly more relaxed grammar for better error reporting and recovery. /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}` /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}` fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness) -> PResult<'a, ItemInfo> { // First, parse generic parameters if necessary. let mut generics = if self.choose_generics_over_qpath() { self.parse_generics()? } else { ast::Generics::default() }; // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type. let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) { self.bump(); // `!` ast::ImplPolarity::Negative } else { ast::ImplPolarity::Positive }; // Parse both types and traits as a type, then reinterpret if necessary. let ty_first = self.parse_ty()?; // If `for` is missing we try to recover. let has_for = self.eat_keyword(keywords::For); let missing_for_span = self.prev_span.between(self.span); let ty_second = if self.token == token::DotDot { // We need to report this error after `cfg` expansion for compatibility reasons self.bump(); // `..`, do not add it to expected tokens Some(P(Ty { node: TyKind::Err, span: self.prev_span, id: ast::DUMMY_NODE_ID })) } else if has_for || self.token.can_begin_type() { Some(self.parse_ty()?) } else { None }; generics.where_clause = self.parse_where_clause()?; let (impl_items, attrs) = self.parse_impl_body()?; let item_kind = match ty_second { Some(ty_second) => { // impl Trait for Type if !has_for { self.struct_span_err(missing_for_span, "missing `for` in a trait impl") .span_suggestion_short( missing_for_span, "add `for` here", " for ".to_string(), Applicability::MachineApplicable, ).emit(); } let ty_first = ty_first.into_inner(); let path = match ty_first.node { // This notably includes paths passed through `ty` macro fragments (#46438). TyKind::Path(None, path) => path, _ => { self.span_err(ty_first.span, "expected a trait, found type"); ast::Path::from_ident(Ident::new(keywords::Invalid.name(), ty_first.span)) } }; let trait_ref = TraitRef { path, ref_id: ty_first.id }; ItemKind::Impl(unsafety, polarity, defaultness, generics, Some(trait_ref), ty_second, impl_items) } None => { // impl Type ItemKind::Impl(unsafety, polarity, defaultness, generics, None, ty_first, impl_items) } }; Ok((keywords::Invalid.ident(), item_kind, Some(attrs))) } fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> { if self.eat_keyword(keywords::For) { self.expect_lt()?; let params = self.parse_generic_params()?; self.expect_gt()?; // We rely on AST validation to rule out invalid cases: There must not be type // parameters, and the lifetime parameters must not have bounds. Ok(params) } else { Ok(Vec::new()) } } /// Parses `struct Foo { ... }`. fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> { let class_name = self.parse_ident()?; let mut generics = self.parse_generics()?; // There is a special case worth noting here, as reported in issue #17904. // If we are parsing a tuple struct it is the case that the where clause // should follow the field list. Like so: // // struct Foo<T>(T) where T: Copy; // // If we are parsing a normal record-style struct it is the case // that the where clause comes before the body, and after the generics. // So if we look ahead and see a brace or a where-clause we begin // parsing a record style struct. // // Otherwise if we look ahead and see a paren we parse a tuple-style // struct. let vdata = if self.token.is_keyword(keywords::Where) { generics.where_clause = self.parse_where_clause()?; if self.eat(&token::Semi) { // If we see a: `struct Foo<T> where T: Copy;` style decl. VariantData::Unit(ast::DUMMY_NODE_ID) } else { // If we see: `struct Foo<T> where T: Copy { ... }` VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID) } // No `where` so: `struct Foo<T>;` } else if self.eat(&token::Semi) { VariantData::Unit(ast::DUMMY_NODE_ID) // Record-style struct definition } else if self.token == token::OpenDelim(token::Brace) { VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID) // Tuple-style struct definition with optional where-clause. } else if self.token == token::OpenDelim(token::Paren) { let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID); generics.where_clause = self.parse_where_clause()?; self.expect(&token::Semi)?; body } else { let token_str = self.this_token_descr(); let mut err = self.fatal(&format!( "expected `where`, `{{`, `(`, or `;` after struct name, found {}", token_str )); err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name"); return Err(err); }; Ok((class_name, ItemKind::Struct(vdata, generics), None)) } /// Parses `union Foo { ... }`. fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> { let class_name = self.parse_ident()?; let mut generics = self.parse_generics()?; let vdata = if self.token.is_keyword(keywords::Where) { generics.where_clause = self.parse_where_clause()?; VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID) } else if self.token == token::OpenDelim(token::Brace) { VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID) } else { let token_str = self.this_token_descr(); let mut err = self.fatal(&format!( "expected `where` or `{{` after union name, found {}", token_str)); err.span_label(self.span, "expected `where` or `{` after union name"); return Err(err); }; Ok((class_name, ItemKind::Union(vdata, generics), None)) } fn consume_block(&mut self, delim: token::DelimToken) { let mut brace_depth = 0; loop { if self.eat(&token::OpenDelim(delim)) { brace_depth += 1; } else if self.eat(&token::CloseDelim(delim)) { if brace_depth == 0 { return; } else { brace_depth -= 1; continue; } } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) { return; } else { self.bump(); } } } fn parse_record_struct_body(&mut self) -> PResult<'a, Vec<StructField>> { let mut fields = Vec::new(); if self.eat(&token::OpenDelim(token::Brace)) { while self.token != token::CloseDelim(token::Brace) { let field = self.parse_struct_decl_field().map_err(|e| { self.recover_stmt(); e }); match field { Ok(field) => fields.push(field), Err(mut err) => { err.emit(); } } } self.eat(&token::CloseDelim(token::Brace)); } else { let token_str = self.this_token_descr(); let mut err = self.fatal(&format!( "expected `where`, or `{{` after struct name, found {}", token_str)); err.span_label(self.span, "expected `where`, or `{` after struct name"); return Err(err); } Ok(fields) } fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> { // This is the case where we find `struct Foo<T>(T) where T: Copy;` // Unit like structs are handled in parse_item_struct function let fields = self.parse_unspanned_seq( &token::OpenDelim(token::Paren), &token::CloseDelim(token::Paren), SeqSep::trailing_allowed(token::Comma), |p| { let attrs = p.parse_outer_attributes()?; let lo = p.span; let vis = p.parse_visibility(true)?; let ty = p.parse_ty()?; Ok(StructField { span: lo.to(ty.span), vis, ident: None, id: ast::DUMMY_NODE_ID, ty, attrs, }) })?; Ok(fields) } /// Parses a structure field declaration. fn parse_single_struct_field(&mut self, lo: Span, vis: Visibility, attrs: Vec<Attribute> ) -> PResult<'a, StructField> { let mut seen_comma: bool = false; let a_var = self.parse_name_and_ty(lo, vis, attrs)?; if self.token == token::Comma { seen_comma = true; } match self.token { token::Comma => { self.bump(); } token::CloseDelim(token::Brace) => {} token::DocComment(_) => { let previous_span = self.prev_span; let mut err = self.span_fatal_err(self.span, Error::UselessDocComment); self.bump(); // consume the doc comment let comma_after_doc_seen = self.eat(&token::Comma); // `seen_comma` is always false, because we are inside doc block // condition is here to make code more readable if seen_comma == false && comma_after_doc_seen == true { seen_comma = true; } if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) { err.emit(); } else { if seen_comma == false { let sp = self.sess.source_map().next_point(previous_span); err.span_suggestion( sp, "missing comma here", ",".into(), Applicability::MachineApplicable ); } return Err(err); } } _ => { let sp = self.sess.source_map().next_point(self.prev_span); let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}", self.this_token_descr())); if self.token.is_ident() { // This is likely another field; emit the diagnostic and keep going err.span_suggestion( sp, "try adding a comma", ",".into(), Applicability::MachineApplicable, ); err.emit(); } else { return Err(err) } } } Ok(a_var) } /// Parses an element of a struct declaration. fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> { let attrs = self.parse_outer_attributes()?; let lo = self.span; let vis = self.parse_visibility(false)?; self.parse_single_struct_field(lo, vis, attrs) } /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`, /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`. /// If the following element can't be a tuple (i.e., it's a function definition), then /// it's not a tuple struct field), and the contents within the parentheses isn't valid, /// so emit a proper diagnostic. pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> { maybe_whole!(self, NtVis, |x| x); self.expected_tokens.push(TokenType::Keyword(keywords::Crate)); if self.is_crate_vis() { self.bump(); // `crate` return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate))); } if !self.eat_keyword(keywords::Pub) { // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no // keyword to grab a span from for inherited visibility; an empty span at the // beginning of the current token would seem to be the "Schelling span". return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited)) } let lo = self.prev_span; if self.check(&token::OpenDelim(token::Paren)) { // We don't `self.bump()` the `(` yet because this might be a struct definition where // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`. // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so // by the following tokens. if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) { // `pub(crate)` self.bump(); // `(` self.bump(); // `crate` self.expect(&token::CloseDelim(token::Paren))?; // `)` let vis = respan( lo.to(self.prev_span), VisibilityKind::Crate(CrateSugar::PubCrate), ); return Ok(vis) } else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) { // `pub(in path)` self.bump(); // `(` self.bump(); // `in` let path = self.parse_path(PathStyle::Mod)?; // `path` self.expect(&token::CloseDelim(token::Paren))?; // `)` let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID, }); return Ok(vis) } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) && self.look_ahead(1, |t| t.is_keyword(keywords::Super) || t.is_keyword(keywords::SelfLower)) { // `pub(self)` or `pub(super)` self.bump(); // `(` let path = self.parse_path(PathStyle::Mod)?; // `super`/`self` self.expect(&token::CloseDelim(token::Paren))?; // `)` let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID, }); return Ok(vis) } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct // `pub(something) fn ...` or `struct X { pub(something) y: Z }` self.bump(); // `(` let msg = "incorrect visibility restriction"; let suggestion = r##"some possible visibility restrictions are: `pub(crate)`: visible only on the current crate `pub(super)`: visible only in the current module's parent `pub(in path::to::module)`: visible only on the specified path"##; let path = self.parse_path(PathStyle::Mod)?; let sp = self.prev_span; let help_msg = format!("make this visible only to module `{}` with `in`", path); self.expect(&token::CloseDelim(token::Paren))?; // `)` let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg); err.help(suggestion); err.span_suggestion( sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable ); err.emit(); // emit diagnostic, but continue with public visibility } } Ok(respan(lo, VisibilityKind::Public)) } /// Parses defaultness (i.e., `default` or nothing). fn parse_defaultness(&mut self) -> Defaultness { // `pub` is included for better error messages if self.check_keyword(keywords::Default) && self.look_ahead(1, |t| t.is_keyword(keywords::Impl) || t.is_keyword(keywords::Const) || t.is_keyword(keywords::Fn) || t.is_keyword(keywords::Unsafe) || t.is_keyword(keywords::Extern) || t.is_keyword(keywords::Type) || t.is_keyword(keywords::Pub)) { self.bump(); // `default` Defaultness::Default } else { Defaultness::Final } } fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool { if self.eat(&token::Semi) { let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`"); err.span_suggestion_short( self.prev_span, "remove this semicolon", String::new(), Applicability::MachineApplicable, ); if !items.is_empty() { let previous_item = &items[items.len()-1]; let previous_item_kind_name = match previous_item.node { // say "braced struct" because tuple-structs and // braceless-empty-struct declarations do take a semicolon ItemKind::Struct(..) => Some("braced struct"), ItemKind::Enum(..) => Some("enum"), ItemKind::Trait(..) => Some("trait"), ItemKind::Union(..) => Some("union"), _ => None, }; if let Some(name) = previous_item_kind_name { err.help(&format!("{} declarations are not followed by a semicolon", name)); } } err.emit(); true } else { false } } /// Given a termination token, parses all of the items in a module. fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> { let mut items = vec![]; while let Some(item) = self.parse_item()? { items.push(item); self.maybe_consume_incorrect_semicolon(&items); } if !self.eat(term) { let token_str = self.this_token_descr(); if !self.maybe_consume_incorrect_semicolon(&items) { let mut err = self.fatal(&format!("expected item, found {}", token_str)); err.span_label(self.span, "expected item"); return Err(err); } } let hi = if self.span.is_dummy() { inner_lo } else { self.prev_span }; Ok(ast::Mod { inner: inner_lo.to(hi), items, inline: true }) } fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> { let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?; self.expect(&token::Colon)?; let ty = self.parse_ty()?; self.expect(&token::Eq)?; let e = self.parse_expr()?; self.expect(&token::Semi)?; let item = match m { Some(m) => ItemKind::Static(ty, m, e), None => ItemKind::Const(ty, e), }; Ok((id, item, None)) } /// Parse a `mod <foo> { ... }` or `mod <foo>;` item fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> { let (in_cfg, outer_attrs) = { let mut strip_unconfigured = crate::config::StripUnconfigured { sess: self.sess, features: None, // don't perform gated feature checking }; let mut outer_attrs = outer_attrs.to_owned(); strip_unconfigured.process_cfg_attrs(&mut outer_attrs); (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs) }; let id_span = self.span; let id = self.parse_ident()?; if self.eat(&token::Semi) { if in_cfg && self.recurse_into_file_modules { // This mod is in an external file. Let's go get it! let ModulePathSuccess { path, directory_ownership, warn } = self.submod_path(id, &outer_attrs, id_span)?; let (module, mut attrs) = self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?; // Record that we fetched the mod from an external file if warn { let attr = Attribute { id: attr::mk_attr_id(), style: ast::AttrStyle::Outer, path: ast::Path::from_ident(Ident::from_str("warn_directory_ownership")), tokens: TokenStream::empty(), is_sugared_doc: false, span: syntax_pos::DUMMY_SP, }; attr::mark_known(&attr); attrs.push(attr); } Ok((id, ItemKind::Mod(module), Some(attrs))) } else { let placeholder = ast::Mod { inner: syntax_pos::DUMMY_SP, items: Vec::new(), inline: false }; Ok((id, ItemKind::Mod(placeholder), None)) } } else { let old_directory = self.directory.clone(); self.push_directory(id, &outer_attrs); self.expect(&token::OpenDelim(token::Brace))?; let mod_inner_lo = self.span; let attrs = self.parse_inner_attributes()?; let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?; self.directory = old_directory; Ok((id, ItemKind::Mod(module), Some(attrs))) } } fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) { if let Some(path) = attr::first_attr_value_str_by_name(attrs, "path") { self.directory.path.to_mut().push(&path.as_str()); self.directory.ownership = DirectoryOwnership::Owned { relative: None }; } else { // We have to push on the current module name in the case of relative // paths in order to ensure that any additional module paths from inline // `mod x { ... }` come after the relative extension. // // For example, a `mod z { ... }` inside `x/y.rs` should set the current // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`. if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership { if let Some(ident) = relative.take() { // remove the relative offset self.directory.path.to_mut().push(ident.as_str()); } } self.directory.path.to_mut().push(&id.as_str()); } } pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> { if let Some(s) = attr::first_attr_value_str_by_name(attrs, "path") { let s = s.as_str(); // On windows, the base path might have the form // `\\?\foo\bar` in which case it does not tolerate // mixed `/` and `\` separators, so canonicalize // `/` to `\`. #[cfg(windows)] let s = s.replace("/", "\\"); Some(dir_path.join(s)) } else { None } } /// Returns a path to a module. pub fn default_submod_path( id: ast::Ident, relative: Option<ast::Ident>, dir_path: &Path, source_map: &SourceMap) -> ModulePath { // If we're in a foo.rs file instead of a mod.rs file, // we need to look for submodules in // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than // `./<id>.rs` and `./<id>/mod.rs`. let relative_prefix_string; let relative_prefix = if let Some(ident) = relative { relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR); &relative_prefix_string } else { "" }; let mod_name = id.to_string(); let default_path_str = format!("{}{}.rs", relative_prefix, mod_name); let secondary_path_str = format!("{}{}{}mod.rs", relative_prefix, mod_name, path::MAIN_SEPARATOR); let default_path = dir_path.join(&default_path_str); let secondary_path = dir_path.join(&secondary_path_str); let default_exists = source_map.file_exists(&default_path); let secondary_exists = source_map.file_exists(&secondary_path); let result = match (default_exists, secondary_exists) { (true, false) => Ok(ModulePathSuccess { path: default_path, directory_ownership: DirectoryOwnership::Owned { relative: Some(id), }, warn: false, }), (false, true) => Ok(ModulePathSuccess { path: secondary_path, directory_ownership: DirectoryOwnership::Owned { relative: None, }, warn: false, }), (false, false) => Err(Error::FileNotFoundForModule { mod_name: mod_name.clone(), default_path: default_path_str, secondary_path: secondary_path_str, dir_path: dir_path.display().to_string(), }), (true, true) => Err(Error::DuplicatePaths { mod_name: mod_name.clone(), default_path: default_path_str, secondary_path: secondary_path_str, }), }; ModulePath { name: mod_name, path_exists: default_exists || secondary_exists, result, } } fn submod_path(&mut self, id: ast::Ident, outer_attrs: &[Attribute], id_sp: Span) -> PResult<'a, ModulePathSuccess> { if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) { return Ok(ModulePathSuccess { directory_ownership: match path.file_name().and_then(|s| s.to_str()) { // All `#[path]` files are treated as though they are a `mod.rs` file. // This means that `mod foo;` declarations inside `#[path]`-included // files are siblings, // // Note that this will produce weirdness when a file named `foo.rs` is // `#[path]` included and contains a `mod foo;` declaration. // If you encounter this, it's your own darn fault :P Some(_) => DirectoryOwnership::Owned { relative: None }, _ => DirectoryOwnership::UnownedViaMod(true), }, path, warn: false, }); } let relative = match self.directory.ownership { DirectoryOwnership::Owned { relative } => relative, DirectoryOwnership::UnownedViaBlock | DirectoryOwnership::UnownedViaMod(_) => None, }; let paths = Parser::default_submod_path( id, relative, &self.directory.path, self.sess.source_map()); match self.directory.ownership { DirectoryOwnership::Owned { .. } => { paths.result.map_err(|err| self.span_fatal_err(id_sp, err)) }, DirectoryOwnership::UnownedViaBlock => { let msg = "Cannot declare a non-inline module inside a block \ unless it has a path attribute"; let mut err = self.diagnostic().struct_span_err(id_sp, msg); if paths.path_exists { let msg = format!("Maybe `use` the module `{}` instead of redeclaring it", paths.name); err.span_note(id_sp, &msg); } Err(err) } DirectoryOwnership::UnownedViaMod(warn) => { if warn { if let Ok(result) = paths.result { return Ok(ModulePathSuccess { warn: true, ..result }); } } let mut err = self.diagnostic().struct_span_err(id_sp, "cannot declare a new module at this location"); if !id_sp.is_dummy() { let src_path = self.sess.source_map().span_to_filename(id_sp); if let FileName::Real(src_path) = src_path { if let Some(stem) = src_path.file_stem() { let mut dest_path = src_path.clone(); dest_path.set_file_name(stem); dest_path.push("mod.rs"); err.span_note(id_sp, &format!("maybe move this module `{}` to its own \ directory via `{}`", src_path.display(), dest_path.display())); } } } if paths.path_exists { err.span_note(id_sp, &format!("... or maybe `use` the module `{}` instead \ of possibly redeclaring it", paths.name)); } Err(err) } } } /// Reads a module from a source file. fn eval_src_mod(&mut self, path: PathBuf, directory_ownership: DirectoryOwnership, name: String, id_sp: Span) -> PResult<'a, (ast::Mod, Vec<Attribute> )> { let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut(); if let Some(i) = included_mod_stack.iter().position(|p| *p == path) { let mut err = String::from("circular modules: "); let len = included_mod_stack.len(); for p in &included_mod_stack[i.. len] { err.push_str(&p.to_string_lossy()); err.push_str(" -> "); } err.push_str(&path.to_string_lossy()); return Err(self.span_fatal(id_sp, &err[..])); } included_mod_stack.push(path.clone()); drop(included_mod_stack); let mut p0 = new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp); p0.cfg_mods = self.cfg_mods; let mod_inner_lo = p0.span; let mod_attrs = p0.parse_inner_attributes()?; let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?; m0.inline = false; self.sess.included_mod_stack.borrow_mut().pop(); Ok((m0, mod_attrs)) } /// Parses a function declaration from a foreign module. fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, ForeignItem> { self.expect_keyword(keywords::Fn)?; let (ident, mut generics) = self.parse_fn_header()?; let decl = self.parse_fn_decl(true)?; generics.where_clause = self.parse_where_clause()?; let hi = self.span; self.expect(&token::Semi)?; Ok(ast::ForeignItem { ident, attrs, node: ForeignItemKind::Fn(decl, generics), id: ast::DUMMY_NODE_ID, span: lo.to(hi), vis, }) } /// Parses a static item from a foreign module. /// Assumes that the `static` keyword is already parsed. fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, ForeignItem> { let mutbl = self.eat_keyword(keywords::Mut); let ident = self.parse_ident()?; self.expect(&token::Colon)?; let ty = self.parse_ty()?; let hi = self.span; self.expect(&token::Semi)?; Ok(ForeignItem { ident, attrs, node: ForeignItemKind::Static(ty, mutbl), id: ast::DUMMY_NODE_ID, span: lo.to(hi), vis, }) } /// Parses a type from a foreign module. fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, ForeignItem> { self.expect_keyword(keywords::Type)?; let ident = self.parse_ident()?; let hi = self.span; self.expect(&token::Semi)?; Ok(ast::ForeignItem { ident: ident, attrs: attrs, node: ForeignItemKind::Ty, id: ast::DUMMY_NODE_ID, span: lo.to(hi), vis: vis }) } fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> { let error_msg = "crate name using dashes are not valid in `extern crate` statements"; let suggestion_msg = "if the original crate name uses dashes you need to use underscores \ in the code"; let mut ident = if self.token.is_keyword(keywords::SelfLower) { self.parse_path_segment_ident() } else { self.parse_ident() }?; let mut idents = vec![]; let mut replacement = vec![]; let mut fixed_crate_name = false; // Accept `extern crate name-like-this` for better diagnostics let dash = token::Token::BinOp(token::BinOpToken::Minus); if self.token == dash { // Do not include `-` as part of the expected tokens list while self.eat(&dash) { fixed_crate_name = true; replacement.push((self.prev_span, "_".to_string())); idents.push(self.parse_ident()?); } } if fixed_crate_name { let fixed_name_sp = ident.span.to(idents.last().unwrap().span); let mut fixed_name = format!("{}", ident.name); for part in idents { fixed_name.push_str(&format!("_{}", part.name)); } ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp); let mut err = self.struct_span_err(fixed_name_sp, error_msg); err.span_label(fixed_name_sp, "dash-separated idents are not valid"); err.multipart_suggestion( suggestion_msg, replacement, Applicability::MachineApplicable, ); err.emit(); } Ok(ident) } /// Parses `extern crate` links. /// /// # Examples /// /// ``` /// extern crate foo; /// extern crate bar as foo; /// ``` fn parse_item_extern_crate(&mut self, lo: Span, visibility: Visibility, attrs: Vec<Attribute>) -> PResult<'a, P<Item>> { // Accept `extern crate name-like-this` for better diagnostics let orig_name = self.parse_crate_name_with_dashes()?; let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? { (rename, Some(orig_name.name)) } else { (orig_name, None) }; self.expect(&token::Semi)?; let span = lo.to(self.prev_span); Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs)) } /// Parses `extern` for foreign ABIs modules. /// /// `extern` is expected to have been /// consumed before calling this method. /// /// # Examples /// /// ```ignore (only-for-syntax-highlight) /// extern "C" {} /// extern {} /// ``` fn parse_item_foreign_mod(&mut self, lo: Span, opt_abi: Option<Abi>, visibility: Visibility, mut attrs: Vec<Attribute>) -> PResult<'a, P<Item>> { self.expect(&token::OpenDelim(token::Brace))?; let abi = opt_abi.unwrap_or(Abi::C); attrs.extend(self.parse_inner_attributes()?); let mut foreign_items = vec![]; while !self.eat(&token::CloseDelim(token::Brace)) { foreign_items.push(self.parse_foreign_item()?); } let prev_span = self.prev_span; let m = ast::ForeignMod { abi, items: foreign_items }; let invalid = keywords::Invalid.ident(); Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs)) } /// Parses `type Foo = Bar;` /// or /// `existential type Foo: Bar;` /// or /// `return `None`` /// without modifying the parser state. fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> { // This parses the grammar: // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";" if self.check_keyword(keywords::Type) || self.check_keyword(keywords::Existential) && self.look_ahead(1, |t| t.is_keyword(keywords::Type)) { let existential = self.eat_keyword(keywords::Existential); assert!(self.eat_keyword(keywords::Type)); Some(self.parse_existential_or_alias(existential)) } else { None } } /// Parses a type alias or existential type. fn parse_existential_or_alias( &mut self, existential: bool, ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> { let ident = self.parse_ident()?; let mut tps = self.parse_generics()?; tps.where_clause = self.parse_where_clause()?; let alias = if existential { self.expect(&token::Colon)?; let bounds = self.parse_generic_bounds(None)?; AliasKind::Existential(bounds) } else { self.expect(&token::Eq)?; let ty = self.parse_ty()?; AliasKind::Weak(ty) }; self.expect(&token::Semi)?; Ok((ident, alias, tps)) } /// Parses the part of an enum declaration following the `{`. fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> { let mut variants = Vec::new(); let mut all_nullary = true; let mut any_disr = vec![]; while self.token != token::CloseDelim(token::Brace) { let variant_attrs = self.parse_outer_attributes()?; let vlo = self.span; let struct_def; let mut disr_expr = None; let ident = self.parse_ident()?; if self.check(&token::OpenDelim(token::Brace)) { // Parse a struct variant. all_nullary = false; struct_def = VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID); } else if self.check(&token::OpenDelim(token::Paren)) { all_nullary = false; struct_def = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID); } else if self.eat(&token::Eq) { disr_expr = Some(AnonConst { id: ast::DUMMY_NODE_ID, value: self.parse_expr()?, }); if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) { any_disr.push(sp); } struct_def = VariantData::Unit(ast::DUMMY_NODE_ID); } else { struct_def = VariantData::Unit(ast::DUMMY_NODE_ID); } let vr = ast::Variant_ { ident, attrs: variant_attrs, data: struct_def, disr_expr, }; variants.push(respan(vlo.to(self.prev_span), vr)); if !self.eat(&token::Comma) { break; } } self.expect(&token::CloseDelim(token::Brace))?; if !any_disr.is_empty() && !all_nullary { let mut err =self.struct_span_err( any_disr.clone(), "discriminator values can only be used with a field-less enum", ); for sp in any_disr { err.span_label(sp, "only valid in field-less enums"); } err.emit(); } Ok(ast::EnumDef { variants }) } /// Parses an enum declaration. fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> { let id = self.parse_ident()?; let mut generics = self.parse_generics()?; generics.where_clause = self.parse_where_clause()?; self.expect(&token::OpenDelim(token::Brace))?; let enum_definition = self.parse_enum_def(&generics).map_err(|e| { self.recover_stmt(); self.eat(&token::CloseDelim(token::Brace)); e })?; Ok((id, ItemKind::Enum(enum_definition, generics), None)) } /// Parses a string as an ABI spec on an extern type or module. Consumes /// the `extern` keyword, if one is found. fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> { match self.token { token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => { let sp = self.span; self.expect_no_suffix(sp, "ABI spec", suf); self.bump(); match abi::lookup(&s.as_str()) { Some(abi) => Ok(Some(abi)), None => { let prev_span = self.prev_span; let mut err = struct_span_err!( self.sess.span_diagnostic, prev_span, E0703, "invalid ABI: found `{}`", s); err.span_label(prev_span, "invalid ABI"); err.help(&format!("valid ABIs: {}", abi::all_names().join(", "))); err.emit(); Ok(None) } } } _ => Ok(None), } } fn is_static_global(&mut self) -> bool { if self.check_keyword(keywords::Static) { // Check if this could be a closure !self.look_ahead(1, |token| { if token.is_keyword(keywords::Move) { return true; } match *token { token::BinOp(token::Or) | token::OrOr => true, _ => false, } }) } else { false } } fn parse_item_( &mut self, attrs: Vec<Attribute>, macros_allowed: bool, attributes_allowed: bool, ) -> PResult<'a, Option<P<Item>>> { let (ret, tokens) = self.collect_tokens(|this| { this.parse_item_implementation(attrs, macros_allowed, attributes_allowed) })?; // Once we've parsed an item and recorded the tokens we got while // parsing we may want to store `tokens` into the item we're about to // return. Note, though, that we specifically didn't capture tokens // related to outer attributes. The `tokens` field here may later be // used with procedural macros to convert this item back into a token // stream, but during expansion we may be removing attributes as we go // along. // // If we've got inner attributes then the `tokens` we've got above holds // these inner attributes. If an inner attribute is expanded we won't // actually remove it from the token stream, so we'll just keep yielding // it (bad!). To work around this case for now we just avoid recording // `tokens` if we detect any inner attributes. This should help keep // expansion correct, but we should fix this bug one day! Ok(ret.map(|item| { item.map(|mut i| { if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) { i.tokens = Some(tokens); } i }) })) } /// Parses one of the items allowed by the flags. fn parse_item_implementation( &mut self, attrs: Vec<Attribute>, macros_allowed: bool, attributes_allowed: bool, ) -> PResult<'a, Option<P<Item>>> { maybe_whole!(self, NtItem, |item| { let mut item = item.into_inner(); let mut attrs = attrs; mem::swap(&mut item.attrs, &mut attrs); item.attrs.extend(attrs); Some(P(item)) }); let lo = self.span; let visibility = self.parse_visibility(false)?; if self.eat_keyword(keywords::Use) { // USE ITEM let item_ = ItemKind::Use(P(self.parse_use_tree()?)); self.expect(&token::Semi)?; let span = lo.to(self.prev_span); let item = self.mk_item(span, keywords::Invalid.ident(), item_, visibility, attrs); return Ok(Some(item)); } if self.eat_keyword(keywords::Extern) { if self.eat_keyword(keywords::Crate) { return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?)); } let opt_abi = self.parse_opt_abi()?; if self.eat_keyword(keywords::Fn) { // EXTERN FUNCTION ITEM let fn_span = self.prev_span; let abi = opt_abi.unwrap_or(Abi::C); let (ident, item_, extra_attrs) = self.parse_item_fn(Unsafety::Normal, IsAsync::NotAsync, respan(fn_span, Constness::NotConst), abi)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } else if self.check(&token::OpenDelim(token::Brace)) { return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?)); } self.unexpected()?; } if self.is_static_global() { self.bump(); // STATIC ITEM let m = if self.eat_keyword(keywords::Mut) { Mutability::Mutable } else { Mutability::Immutable }; let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.eat_keyword(keywords::Const) { let const_span = self.prev_span; if self.check_keyword(keywords::Fn) || (self.check_keyword(keywords::Unsafe) && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) { // CONST FUNCTION ITEM let unsafety = self.parse_unsafety(); self.bump(); let (ident, item_, extra_attrs) = self.parse_item_fn(unsafety, IsAsync::NotAsync, respan(const_span, Constness::Const), Abi::Rust)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } // CONST ITEM if self.eat_keyword(keywords::Mut) { let prev_span = self.prev_span; let mut err = self.diagnostic() .struct_span_err(prev_span, "const globals cannot be mutable"); err.span_label(prev_span, "cannot be mutable"); err.span_suggestion( const_span, "you might want to declare a static instead", "static".to_owned(), Applicability::MaybeIncorrect, ); err.emit(); } let (ident, item_, extra_attrs) = self.parse_item_const(None)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } // `unsafe async fn` or `async fn` if ( self.check_keyword(keywords::Unsafe) && self.look_ahead(1, |t| t.is_keyword(keywords::Async)) ) || ( self.check_keyword(keywords::Async) && self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) ) { // ASYNC FUNCTION ITEM let unsafety = self.parse_unsafety(); self.expect_keyword(keywords::Async)?; self.expect_keyword(keywords::Fn)?; let fn_span = self.prev_span; let (ident, item_, extra_attrs) = self.parse_item_fn(unsafety, IsAsync::Async { closure_id: ast::DUMMY_NODE_ID, return_impl_trait_id: ast::DUMMY_NODE_ID, }, respan(fn_span, Constness::NotConst), Abi::Rust)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.check_keyword(keywords::Unsafe) && (self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) || self.look_ahead(1, |t| t.is_keyword(keywords::Auto))) { // UNSAFE TRAIT ITEM self.bump(); // `unsafe` let is_auto = if self.eat_keyword(keywords::Trait) { IsAuto::No } else { self.expect_keyword(keywords::Auto)?; self.expect_keyword(keywords::Trait)?; IsAuto::Yes }; let (ident, item_, extra_attrs) = self.parse_item_trait(is_auto, Unsafety::Unsafe)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.check_keyword(keywords::Impl) || self.check_keyword(keywords::Unsafe) && self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) || self.check_keyword(keywords::Default) && self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) || self.check_keyword(keywords::Default) && self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) { // IMPL ITEM let defaultness = self.parse_defaultness(); let unsafety = self.parse_unsafety(); self.expect_keyword(keywords::Impl)?; let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?; let span = lo.to(self.prev_span); return Ok(Some(self.mk_item(span, ident, item, visibility, maybe_append(attrs, extra_attrs)))); } if self.check_keyword(keywords::Fn) { // FUNCTION ITEM self.bump(); let fn_span = self.prev_span; let (ident, item_, extra_attrs) = self.parse_item_fn(Unsafety::Normal, IsAsync::NotAsync, respan(fn_span, Constness::NotConst), Abi::Rust)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.check_keyword(keywords::Unsafe) && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) { // UNSAFE FUNCTION ITEM self.bump(); // `unsafe` // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic self.check(&token::OpenDelim(token::Brace)); let abi = if self.eat_keyword(keywords::Extern) { self.parse_opt_abi()?.unwrap_or(Abi::C) } else { Abi::Rust }; self.expect_keyword(keywords::Fn)?; let fn_span = self.prev_span; let (ident, item_, extra_attrs) = self.parse_item_fn(Unsafety::Unsafe, IsAsync::NotAsync, respan(fn_span, Constness::NotConst), abi)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.eat_keyword(keywords::Mod) { // MODULE ITEM let (ident, item_, extra_attrs) = self.parse_item_mod(&attrs[..])?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if let Some(type_) = self.eat_type() { let (ident, alias, generics) = type_?; // TYPE ITEM let item_ = match alias { AliasKind::Weak(ty) => ItemKind::Ty(ty, generics), AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics), }; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, attrs); return Ok(Some(item)); } if self.eat_keyword(keywords::Enum) { // ENUM ITEM let (ident, item_, extra_attrs) = self.parse_item_enum()?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.check_keyword(keywords::Trait) || (self.check_keyword(keywords::Auto) && self.look_ahead(1, |t| t.is_keyword(keywords::Trait))) { let is_auto = if self.eat_keyword(keywords::Trait) { IsAuto::No } else { self.expect_keyword(keywords::Auto)?; self.expect_keyword(keywords::Trait)?; IsAuto::Yes }; // TRAIT ITEM let (ident, item_, extra_attrs) = self.parse_item_trait(is_auto, Unsafety::Normal)?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.eat_keyword(keywords::Struct) { // STRUCT ITEM let (ident, item_, extra_attrs) = self.parse_item_struct()?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if self.is_union_item() { // UNION ITEM self.bump(); let (ident, item_, extra_attrs) = self.parse_item_union()?; let prev_span = self.prev_span; let item = self.mk_item(lo.to(prev_span), ident, item_, visibility, maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? { return Ok(Some(macro_def)); } // Verify whether we have encountered a struct or method definition where the user forgot to // add the `struct` or `fn` keyword after writing `pub`: `pub S {}` if visibility.node.is_pub() && self.check_ident() && self.look_ahead(1, |t| *t != token::Not) { // Space between `pub` keyword and the identifier // // pub S {} // ^^^ `sp` points here let sp = self.prev_span.between(self.span); let full_sp = self.prev_span.to(self.span); let ident_sp = self.span; if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) { // possible public struct definition where `struct` was forgotten let ident = self.parse_ident().unwrap(); let msg = format!("add `struct` here to parse `{}` as a public struct", ident); let mut err = self.diagnostic() .struct_span_err(sp, "missing `struct` for struct definition"); err.span_suggestion_short( sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative ); return Err(err); } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) { let ident = self.parse_ident().unwrap(); self.bump(); // `(` let kw_name = if let Ok(Some(_)) = self.parse_self_arg() { "method" } else { "function" }; self.consume_block(token::Paren); let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) { self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]); self.bump(); // `{` ("fn", kw_name, false) } else if self.check(&token::OpenDelim(token::Brace)) { self.bump(); // `{` ("fn", kw_name, false) } else if self.check(&token::Colon) { let kw = "struct"; (kw, kw, false) } else { ("fn` or `struct", "function or struct", true) }; self.consume_block(token::Brace); let msg = format!("missing `{}` for {} definition", kw, kw_name); let mut err = self.diagnostic().struct_span_err(sp, &msg); if !ambiguous { let suggestion = format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name); err.span_suggestion_short( sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable ); } else { if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) { err.span_suggestion( full_sp, "if you meant to call a macro, try", format!("{}!", snippet), // this is the `ambiguous` conditional branch Applicability::MaybeIncorrect ); } else { err.help("if you meant to call a macro, remove the `pub` \ and add a trailing `!` after the identifier"); } } return Err(err); } else if self.look_ahead(1, |t| *t == token::Lt) { let ident = self.parse_ident().unwrap(); self.eat_to_tokens(&[&token::Gt]); self.bump(); // `>` let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) { if let Ok(Some(_)) = self.parse_self_arg() { ("fn", "method", false) } else { ("fn", "function", false) } } else if self.check(&token::OpenDelim(token::Brace)) { ("struct", "struct", false) } else { ("fn` or `struct", "function or struct", true) }; let msg = format!("missing `{}` for {} definition", kw, kw_name); let mut err = self.diagnostic().struct_span_err(sp, &msg); if !ambiguous { err.span_suggestion_short( sp, &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name), format!(" {} ", kw), Applicability::MachineApplicable, ); } return Err(err); } } self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility) } /// Parses a foreign item. crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> { maybe_whole!(self, NtForeignItem, |ni| ni); let attrs = self.parse_outer_attributes()?; let lo = self.span; let visibility = self.parse_visibility(false)?; // FOREIGN STATIC ITEM // Treat `const` as `static` for error recovery, but don't add it to expected tokens. if self.check_keyword(keywords::Static) || self.token.is_keyword(keywords::Const) { if self.token.is_keyword(keywords::Const) { self.diagnostic() .struct_span_err(self.span, "extern items cannot be `const`") .span_suggestion( self.span, "try using a static value", "static".to_owned(), Applicability::MachineApplicable ).emit(); } self.bump(); // `static` or `const` return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?); } // FOREIGN FUNCTION ITEM if self.check_keyword(keywords::Fn) { return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?); } // FOREIGN TYPE ITEM if self.check_keyword(keywords::Type) { return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?); } match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? { Some(mac) => { Ok( ForeignItem { ident: keywords::Invalid.ident(), span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID, attrs, vis: visibility, node: ForeignItemKind::Macro(mac), } ) } None => { if !attrs.is_empty() { self.expected_item_err(&attrs)?; } self.unexpected() } } } /// This is the fall-through for parsing items. fn parse_macro_use_or_failure( &mut self, attrs: Vec<Attribute> , macros_allowed: bool, attributes_allowed: bool, lo: Span, visibility: Visibility ) -> PResult<'a, Option<P<Item>>> { if macros_allowed && self.token.is_path_start() { // MACRO INVOCATION ITEM let prev_span = self.prev_span; self.complain_if_pub_macro(&visibility.node, prev_span); let mac_lo = self.span; // item macro. let pth = self.parse_path(PathStyle::Mod)?; self.expect(&token::Not)?; // a 'special' identifier (like what `macro_rules!` uses) // is optional. We should eventually unify invoc syntax // and remove this. let id = if self.token.is_ident() { self.parse_ident()? } else { keywords::Invalid.ident() // no special identifier }; // eat a matched-delimiter token tree: let (delim, tts) = self.expect_delimited_token_tree()?; if delim != MacDelimiter::Brace { if !self.eat(&token::Semi) { self.span_err(self.prev_span, "macros that expand to items must either \ be surrounded with braces or followed by \ a semicolon"); } } let hi = self.prev_span; let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim }); let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs); return Ok(Some(item)); } // FAILURE TO PARSE ITEM match visibility.node { VisibilityKind::Inherited => {} _ => { return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`")); } } if !attributes_allowed && !attrs.is_empty() { self.expected_item_err(&attrs)?; } Ok(None) } /// Parses a macro invocation inside a `trait`, `impl` or `extern` block. fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>, at_end: &mut bool) -> PResult<'a, Option<Mac>> { if self.token.is_path_start() { let prev_span = self.prev_span; let lo = self.span; let pth = self.parse_path(PathStyle::Mod)?; if pth.segments.len() == 1 { if !self.eat(&token::Not) { return Err(self.missing_assoc_item_kind_err(item_kind, prev_span)); } } else { self.expect(&token::Not)?; } if let Some(vis) = vis { self.complain_if_pub_macro(&vis.node, prev_span); } *at_end = true; // eat a matched-delimiter token tree: let (delim, tts) = self.expect_delimited_token_tree()?; if delim != MacDelimiter::Brace { self.expect(&token::Semi)?; } Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim }))) } else { Ok(None) } } fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)> where F: FnOnce(&mut Self) -> PResult<'a, R> { // Record all tokens we parse when parsing this item. let mut tokens = Vec::new(); let prev_collecting = match self.token_cursor.frame.last_token { LastToken::Collecting(ref mut list) => { Some(mem::replace(list, Vec::new())) } LastToken::Was(ref mut last) => { tokens.extend(last.take()); None } }; self.token_cursor.frame.last_token = LastToken::Collecting(tokens); let prev = self.token_cursor.stack.len(); let ret = f(self); let last_token = if self.token_cursor.stack.len() == prev { &mut self.token_cursor.frame.last_token } else { &mut self.token_cursor.stack[prev].last_token }; // Pull out the tokens that we've collected from the call to `f` above. let mut collected_tokens = match *last_token { LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()), LastToken::Was(_) => panic!("our vector went away?"), }; // If we're not at EOF our current token wasn't actually consumed by // `f`, but it'll still be in our list that we pulled out. In that case // put it back. let extra_token = if self.token != token::Eof { collected_tokens.pop() } else { None }; // If we were previously collecting tokens, then this was a recursive // call. In that case we need to record all the tokens we collected in // our parent list as well. To do that we push a clone of our stream // onto the previous list. match prev_collecting { Some(mut list) => { list.extend(collected_tokens.iter().cloned()); list.extend(extra_token); *last_token = LastToken::Collecting(list); } None => { *last_token = LastToken::Was(extra_token); } } Ok((ret?, TokenStream::new(collected_tokens))) } pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> { let attrs = self.parse_outer_attributes()?; self.parse_item_(attrs, true, false) } /// `::{` or `::*` fn is_import_coupler(&mut self) -> bool { self.check(&token::ModSep) && self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) || *t == token::BinOp(token::Star)) } /// Parses a `UseTree`. /// /// ``` /// USE_TREE = [`::`] `*` | /// [`::`] `{` USE_TREE_LIST `}` | /// PATH `::` `*` | /// PATH `::` `{` USE_TREE_LIST `}` | /// PATH [`as` IDENT] /// ``` fn parse_use_tree(&mut self) -> PResult<'a, UseTree> { let lo = self.span; let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() }; let kind = if self.check(&token::OpenDelim(token::Brace)) || self.check(&token::BinOp(token::Star)) || self.is_import_coupler() { // `use *;` or `use ::*;` or `use {...};` or `use ::{...};` let mod_sep_ctxt = self.span.ctxt(); if self.eat(&token::ModSep) { prefix.segments.push( PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)) ); } if self.eat(&token::BinOp(token::Star)) { UseTreeKind::Glob } else { UseTreeKind::Nested(self.parse_use_tree_list()?) } } else { // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;` prefix = self.parse_path(PathStyle::Mod)?; if self.eat(&token::ModSep) { if self.eat(&token::BinOp(token::Star)) { UseTreeKind::Glob } else { UseTreeKind::Nested(self.parse_use_tree_list()?) } } else { UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID) } }; Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) }) } /// Parses a `UseTreeKind::Nested(list)`. /// /// ``` /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`] /// ``` fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> { self.parse_unspanned_seq(&token::OpenDelim(token::Brace), &token::CloseDelim(token::Brace), SeqSep::trailing_allowed(token::Comma), |this| { Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID)) }) } fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> { if self.eat_keyword(keywords::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) } } /// Parses a source module as a crate. This is the main entry point for the parser. pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> { let lo = self.span; let krate = Ok(ast::Crate { attrs: self.parse_inner_attributes()?, module: self.parse_mod_items(&token::Eof, lo)?, span: lo.to(self.span), }); emit_unclosed_delims(&self.unclosed_delims, self.diagnostic()); self.unclosed_delims.clear(); krate } pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> { let ret = match self.token { token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf), token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf), _ => return None }; self.bump(); Some(ret) } pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> { match self.parse_optional_str() { Some((s, style, suf)) => { let sp = self.prev_span; self.expect_no_suffix(sp, "string literal", suf); Ok((s, style)) } _ => { let msg = "expected string literal"; let mut err = self.fatal(msg); err.span_label(self.span, msg); Err(err) } } } } pub fn emit_unclosed_delims(unclosed_delims: &[UnmatchedBrace], handler: &errors::Handler) { for unmatched in unclosed_delims { let mut err = handler.struct_span_err(unmatched.found_span, &format!( "incorrect close delimiter: `{}`", pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)), )); err.span_label(unmatched.found_span, "incorrect close delimiter"); if let Some(sp) = unmatched.candidate_span { err.span_label(sp, "close delimiter possibly meant for this"); } if let Some(sp) = unmatched.unclosed_span { err.span_label(sp, "un-closed delimiter"); } err.emit(); } }