rust-clippy/tests/ui/auxiliary/proc_macros.rs

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//@compile-flags: --emit=link
//@no-prefer-dynamic
#![crate_type = "proc-macro"]
#![feature(let_chains)]
#![feature(proc_macro_span)]
2023-06-10 11:43:30 +00:00
#![allow(clippy::needless_if, dead_code)]
extern crate proc_macro;
use core::mem;
use proc_macro::{
token_stream::IntoIter,
Delimiter::{self, Brace, Parenthesis},
Group, Ident, Literal, Punct,
Spacing::{self, Alone, Joint},
Span, TokenStream, TokenTree as TT,
};
type Result<T> = core::result::Result<T, TokenStream>;
/// Make a `compile_error!` pointing to the given span.
fn make_error(msg: &str, span: Span) -> TokenStream {
TokenStream::from_iter([
TT::Ident(Ident::new("compile_error", span)),
TT::Punct(punct_with_span('!', Alone, span)),
TT::Group({
let mut msg = Literal::string(msg);
msg.set_span(span);
group_with_span(Parenthesis, TokenStream::from_iter([TT::Literal(msg)]), span)
}),
])
}
fn expect_tt<T>(tt: Option<TT>, f: impl FnOnce(TT) -> Option<T>, expected: &str, span: Span) -> Result<T> {
match tt {
None => Err(make_error(
&format!("unexpected end of input, expected {expected}"),
span,
)),
Some(tt) => {
let span = tt.span();
match f(tt) {
Some(x) => Ok(x),
None => Err(make_error(&format!("unexpected token, expected {expected}"), span)),
}
},
}
}
fn punct_with_span(c: char, spacing: Spacing, span: Span) -> Punct {
let mut p = Punct::new(c, spacing);
p.set_span(span);
p
}
fn group_with_span(delimiter: Delimiter, stream: TokenStream, span: Span) -> Group {
let mut g = Group::new(delimiter, stream);
g.set_span(span);
g
}
/// Token used to escape the following token from the macro's span rules.
const ESCAPE_CHAR: char = '$';
/// Takes a single token followed by a sequence of tokens. Returns the sequence of tokens with their
/// span set to that of the first token. Tokens may be escaped with either `#ident` or `#(tokens)`.
#[proc_macro]
pub fn with_span(input: TokenStream) -> TokenStream {
let mut iter = input.into_iter();
let span = iter.next().unwrap().span();
let mut res = TokenStream::new();
if let Err(e) = write_with_span(span, iter, &mut res) {
e
} else {
res
}
}
/// Takes a sequence of tokens and return the tokens with the span set such that they appear to be
/// from an external macro. Tokens may be escaped with either `#ident` or `#(tokens)`.
#[proc_macro]
pub fn external(input: TokenStream) -> TokenStream {
let mut res = TokenStream::new();
if let Err(e) = write_with_span(Span::mixed_site(), input.into_iter(), &mut res) {
e
} else {
res
}
}
/// Copies all the tokens, replacing all their spans with the given span. Tokens can be escaped
/// either by `#ident` or `#(tokens)`.
fn write_with_span(s: Span, mut input: IntoIter, out: &mut TokenStream) -> Result<()> {
while let Some(tt) = input.next() {
match tt {
TT::Punct(p) if p.as_char() == ESCAPE_CHAR => {
expect_tt(
input.next(),
|tt| match tt {
tt @ (TT::Ident(_) | TT::Literal(_)) => {
out.extend([tt]);
Some(())
},
TT::Punct(mut p) if p.as_char() == ESCAPE_CHAR => {
p.set_span(s);
out.extend([TT::Punct(p)]);
Some(())
},
TT::Group(g) if g.delimiter() == Parenthesis => {
out.extend([TT::Group(group_with_span(Delimiter::None, g.stream(), g.span()))]);
Some(())
},
_ => None,
},
"an ident, a literal, or parenthesized tokens",
p.span(),
)?;
},
TT::Group(g) => {
let mut stream = TokenStream::new();
write_with_span(s, g.stream().into_iter(), &mut stream)?;
out.extend([TT::Group(group_with_span(g.delimiter(), stream, s))]);
},
mut tt => {
tt.set_span(s);
out.extend([tt]);
},
}
}
Ok(())
}
/// Within the item this attribute is attached to, an `inline!` macro is available which expands the
/// contained tokens as though they came from a macro expansion.
///
/// Within the `inline!` macro, any token preceded by `$` is passed as though it were an argument
/// with an automatically chosen fragment specifier. `$ident` will be passed as `ident`, `$1` or
/// `$"literal"` will be passed as `literal`, `$'lt` will be passed as `lifetime`, and `$(...)` will
/// pass the contained tokens as a `tt` sequence (the wrapping parenthesis are removed). If another
/// specifier is required it can be specified within parenthesis like `$(@expr ...)`. This will
/// expand the remaining tokens as a single argument.
///
/// Multiple `inline!` macros may be nested within each other. This will expand as nested macro
/// calls. However, any arguments will be passed as though they came from the outermost context.
#[proc_macro_attribute]
pub fn inline_macros(args: TokenStream, input: TokenStream) -> TokenStream {
let mut args = args.into_iter();
let mac_name = match args.next() {
Some(TT::Ident(name)) => Some(name),
Some(tt) => {
return make_error(
"unexpected argument, expected either an ident or no arguments",
tt.span(),
);
},
None => None,
};
if let Some(tt) = args.next() {
return make_error(
"unexpected argument, expected either an ident or no arguments",
tt.span(),
);
};
let mac_name = if let Some(mac_name) = mac_name {
Ident::new(&format!("__inline_mac_{mac_name}"), Span::call_site())
} else {
let mut input = match LookaheadIter::new(input.clone().into_iter()) {
Some(x) => x,
None => return input,
};
loop {
match input.next() {
None => break Ident::new("__inline_mac", Span::call_site()),
Some(TT::Ident(kind)) => match &*kind.to_string() {
"impl" => break Ident::new("__inline_mac_impl", Span::call_site()),
kind @ ("struct" | "enum" | "union" | "fn" | "mod" | "trait" | "type" | "const" | "static") => {
if let TT::Ident(name) = &input.tt {
break Ident::new(&format!("__inline_mac_{kind}_{name}"), Span::call_site());
} else {
break Ident::new(&format!("__inline_mac_{kind}"), Span::call_site());
}
},
_ => {},
},
_ => {},
}
}
};
let mut expander = Expander::default();
let mut mac = MacWriter::new(mac_name);
if let Err(e) = expander.expand(input.into_iter(), &mut mac) {
return e;
}
let mut out = TokenStream::new();
mac.finish(&mut out);
out.extend(expander.expn);
out
}
/// Wraps a `TokenStream` iterator with a single token lookahead.
struct LookaheadIter {
tt: TT,
iter: IntoIter,
}
impl LookaheadIter {
fn new(mut iter: IntoIter) -> Option<Self> {
iter.next().map(|tt| Self { tt, iter })
}
/// Get's the lookahead token, replacing it with the next token in the stream.
/// Note: If there isn't a next token, this will not return the lookahead token.
fn next(&mut self) -> Option<TT> {
self.iter.next().map(|tt| mem::replace(&mut self.tt, tt))
}
}
/// Builds the macro used to implement all the `inline!` macro calls.
struct MacWriter {
name: Ident,
macros: TokenStream,
next_idx: usize,
}
impl MacWriter {
fn new(name: Ident) -> Self {
Self {
name,
macros: TokenStream::new(),
next_idx: 0,
}
}
/// Inserts a new `inline!` call.
fn insert(&mut self, name_span: Span, bang_span: Span, body: Group, expander: &mut Expander) -> Result<()> {
let idx = self.next_idx;
self.next_idx += 1;
let mut inner = Expander::for_arm(idx);
inner.expand(body.stream().into_iter(), self)?;
let new_arm = inner.arm.unwrap();
self.macros.extend([
TT::Group(Group::new(Parenthesis, new_arm.args_def)),
TT::Punct(Punct::new('=', Joint)),
TT::Punct(Punct::new('>', Alone)),
TT::Group(Group::new(Parenthesis, inner.expn)),
TT::Punct(Punct::new(';', Alone)),
]);
expander.expn.extend([
TT::Ident({
let mut name = self.name.clone();
name.set_span(name_span);
name
}),
TT::Punct(punct_with_span('!', Alone, bang_span)),
]);
let mut call_body = TokenStream::from_iter([TT::Literal(Literal::usize_unsuffixed(idx))]);
if let Some(arm) = expander.arm.as_mut() {
if !new_arm.args.is_empty() {
arm.add_sub_args(new_arm.args, &mut call_body);
}
} else {
call_body.extend(new_arm.args);
}
let mut g = Group::new(body.delimiter(), call_body);
g.set_span(body.span());
expander.expn.extend([TT::Group(g)]);
Ok(())
}
/// Creates the macro definition.
fn finish(self, out: &mut TokenStream) {
if self.next_idx != 0 {
out.extend([
TT::Ident(Ident::new("macro_rules", Span::call_site())),
TT::Punct(Punct::new('!', Alone)),
TT::Ident(self.name),
TT::Group(Group::new(Brace, self.macros)),
])
}
}
}
struct MacroArm {
args_def: TokenStream,
args: Vec<TT>,
}
impl MacroArm {
fn add_single_arg_def(&mut self, kind: &str, dollar_span: Span, arg_span: Span, out: &mut TokenStream) {
let mut name = Ident::new(&format!("_{}", self.args.len()), Span::call_site());
self.args_def.extend([
TT::Punct(Punct::new('$', Alone)),
TT::Ident(name.clone()),
TT::Punct(Punct::new(':', Alone)),
TT::Ident(Ident::new(kind, Span::call_site())),
]);
name.set_span(arg_span);
out.extend([TT::Punct(punct_with_span('$', Alone, dollar_span)), TT::Ident(name)]);
}
fn add_parenthesized_arg_def(&mut self, kind: Ident, dollar_span: Span, arg_span: Span, out: &mut TokenStream) {
let mut name = Ident::new(&format!("_{}", self.args.len()), Span::call_site());
self.args_def.extend([TT::Group(Group::new(
Parenthesis,
TokenStream::from_iter([
TT::Punct(Punct::new('$', Alone)),
TT::Ident(name.clone()),
TT::Punct(Punct::new(':', Alone)),
TT::Ident(kind),
]),
))]);
name.set_span(arg_span);
out.extend([TT::Punct(punct_with_span('$', Alone, dollar_span)), TT::Ident(name)]);
}
fn add_multi_arg_def(&mut self, dollar_span: Span, arg_span: Span, out: &mut TokenStream) {
let mut name = Ident::new(&format!("_{}", self.args.len()), Span::call_site());
self.args_def.extend([TT::Group(Group::new(
Parenthesis,
TokenStream::from_iter([
TT::Punct(Punct::new('$', Alone)),
TT::Group(Group::new(
Parenthesis,
TokenStream::from_iter([
TT::Punct(Punct::new('$', Alone)),
TT::Ident(name.clone()),
TT::Punct(Punct::new(':', Alone)),
TT::Ident(Ident::new("tt", Span::call_site())),
]),
)),
TT::Punct(Punct::new('*', Alone)),
]),
))]);
name.set_span(arg_span);
out.extend([
TT::Punct(punct_with_span('$', Alone, dollar_span)),
TT::Group(group_with_span(
Parenthesis,
TokenStream::from_iter([TT::Punct(punct_with_span('$', Alone, dollar_span)), TT::Ident(name)]),
dollar_span,
)),
TT::Punct(punct_with_span('*', Alone, dollar_span)),
]);
}
fn add_arg(&mut self, dollar_span: Span, tt: TT, input: &mut IntoIter, out: &mut TokenStream) -> Result<()> {
match tt {
TT::Punct(p) if p.as_char() == ESCAPE_CHAR => out.extend([TT::Punct(p)]),
TT::Punct(p) if p.as_char() == '\'' && p.spacing() == Joint => {
let lt_name = expect_tt(
input.next(),
|tt| match tt {
TT::Ident(x) => Some(x),
_ => None,
},
"lifetime name",
p.span(),
)?;
let arg_span = p.span().join(lt_name.span()).unwrap_or(p.span());
self.add_single_arg_def("lifetime", dollar_span, arg_span, out);
self.args.extend([TT::Punct(p), TT::Ident(lt_name)]);
},
TT::Ident(x) => {
self.add_single_arg_def("ident", dollar_span, x.span(), out);
self.args.push(TT::Ident(x));
},
TT::Literal(x) => {
self.add_single_arg_def("literal", dollar_span, x.span(), out);
self.args.push(TT::Literal(x));
},
TT::Group(g) if g.delimiter() == Parenthesis => {
let mut inner = g.stream().into_iter();
if let Some(TT::Punct(p)) = inner.next()
&& p.as_char() == '@'
{
let kind = expect_tt(
inner.next(),
|tt| match tt {
TT::Ident(kind) => Some(kind),
_ => None,
},
"a macro fragment specifier",
p.span(),
)?;
self.add_parenthesized_arg_def(kind, dollar_span, g.span(), out);
self.args.push(TT::Group(group_with_span(Parenthesis, inner.collect(), g.span())))
} else {
self.add_multi_arg_def(dollar_span, g.span(), out);
self.args.push(TT::Group(g));
}
},
tt => return Err(make_error("unsupported escape", tt.span())),
};
Ok(())
}
fn add_sub_args(&mut self, args: Vec<TT>, out: &mut TokenStream) {
self.add_multi_arg_def(Span::call_site(), Span::call_site(), out);
self.args
.extend([TT::Group(Group::new(Parenthesis, TokenStream::from_iter(args)))]);
}
}
#[derive(Default)]
struct Expander {
arm: Option<MacroArm>,
expn: TokenStream,
}
impl Expander {
fn for_arm(idx: usize) -> Self {
Self {
arm: Some(MacroArm {
args_def: TokenStream::from_iter([TT::Literal(Literal::usize_unsuffixed(idx))]),
args: Vec::new(),
}),
expn: TokenStream::new(),
}
}
fn write_tt(&mut self, tt: TT, mac: &mut MacWriter) -> Result<()> {
match tt {
TT::Group(g) => {
let outer = mem::take(&mut self.expn);
self.expand(g.stream().into_iter(), mac)?;
let inner = mem::replace(&mut self.expn, outer);
self.expn
.extend([TT::Group(group_with_span(g.delimiter(), inner, g.span()))]);
},
tt => self.expn.extend([tt]),
}
Ok(())
}
fn expand(&mut self, input: IntoIter, mac: &mut MacWriter) -> Result<()> {
let Some(mut input) = LookaheadIter::new(input) else {
return Ok(());
};
while let Some(tt) = input.next() {
if let TT::Punct(p) = &tt
&& p.as_char() == ESCAPE_CHAR
&& let Some(arm) = self.arm.as_mut()
{
arm.add_arg(p.span(), mem::replace(&mut input.tt, tt), &mut input.iter, &mut self.expn)?;
if input.next().is_none() {
return Ok(());
}
} else if let TT::Punct(p) = &input.tt
&& p.as_char() == '!'
&& let TT::Ident(name) = &tt
&& name.to_string() == "inline"
{
let g = expect_tt(
input.iter.next(),
|tt| match tt {
TT::Group(g) => Some(g),
_ => None,
},
"macro arguments",
p.span(),
)?;
mac.insert(name.span(), p.span(), g, self)?;
if input.next().is_none() {
return Ok(());
}
} else {
self.write_tt(tt, mac)?;
}
}
self.write_tt(input.tt, mac)
}
}