move lexing to the parser crate

Cargo.lock

@@ -1066,7 +1066,9 @@ name = "parser"
 version = "0.0.0"
 dependencies = [
  "drop_bomb",
+ "expect-test",
  "limit",
+ "rustc-ap-rustc_lexer",
 ]
 
 [[package]]

crates/parser/Cargo.toml

@@ -11,5 +11,8 @@ doctest = false
 
 [dependencies]
 drop_bomb = "0.1.4"
-
+rustc_lexer = { version = "725.0.0", package = "rustc-ap-rustc_lexer" }
 limit = { path = "../limit", version = "0.0.0" }
+
+[dev-dependencies]
+expect-test = "1.2"

crates/parser/src/lexer_token.rs

@@ -0,0 +1,210 @@
+//! Lexing `&str` into a sequence of Rust tokens.
+//!
+//! Note that strictly speaking the parser in this crate is not required to work
+//! on tokens which originated from text. Macros, eg, can synthesize tokes out
+//! of thin air. So, ideally, lexer should be an orthogonal crate. It is however
+//! convenient to include a text-based lexer here!
+
+use crate::{
+    SyntaxKind::{self, *},
+    T,
+};
+
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct LexerToken {
+    pub kind: SyntaxKind,
+    pub len: usize,
+    pub error: Option<String>,
+}
+
+impl LexerToken {
+    pub fn new(kind: SyntaxKind, len: usize) -> Self {
+        Self { kind, len, error: None }
+    }
+
+    /// Lexes text as a sequence of tokens.
+    pub fn tokenize(text: &str) -> Vec<LexerToken> {
+        let mut res = Vec::new();
+        let mut offset = 0;
+
+        if let Some(shebang_len) = rustc_lexer::strip_shebang(text) {
+            res.push(LexerToken::new(SHEBANG, shebang_len));
+            offset = shebang_len
+        };
+
+        for token in rustc_lexer::tokenize(&text[offset..]) {
+            let token_text = &text[offset..][..token.len];
+            offset += token.len;
+
+            let (kind, err) = from_rustc(&token.kind, token_text);
+            let mut token = LexerToken::new(kind, token.len);
+            token.error = err.map(|it| it.to_string());
+            res.push(token);
+        }
+
+        res
+    }
+    /// Lexes text as a single token. Returns `None` if there's leftover text.
+    pub fn from_str(text: &str) -> Option<LexerToken> {
+        if text.is_empty() {
+            return None;
+        }
+
+        let token = rustc_lexer::first_token(text);
+        if token.len != text.len() {
+            return None;
+        }
+
+        let (kind, err) = from_rustc(&token.kind, text);
+
+        let mut token = LexerToken::new(kind, token.len);
+        token.error = err.map(|it| it.to_string());
+        Some(token)
+    }
+}
+
+/// Returns `SyntaxKind` and an optional tokenize error message.
+fn from_rustc(
+    kind: &rustc_lexer::TokenKind,
+    token_text: &str,
+) -> (SyntaxKind, Option<&'static str>) {
+    // A note on an intended tradeoff:
+    // We drop some useful information here (see patterns with double dots `..`)
+    // Storing that info in `SyntaxKind` is not possible due to its layout requirements of
+    // being `u16` that come from `rowan::SyntaxKind`.
+    let mut err = "";
+
+    let syntax_kind = {
+        match kind {
+            rustc_lexer::TokenKind::LineComment { doc_style: _ } => COMMENT,
+            rustc_lexer::TokenKind::BlockComment { doc_style: _, terminated } => {
+                if !terminated {
+                    err = "Missing trailing `*/` symbols to terminate the block comment";
+                }
+                COMMENT
+            }
+
+            rustc_lexer::TokenKind::Whitespace => WHITESPACE,
+
+            rustc_lexer::TokenKind::Ident if token_text == "_" => UNDERSCORE,
+            rustc_lexer::TokenKind::Ident => SyntaxKind::from_keyword(token_text).unwrap_or(IDENT),
+
+            rustc_lexer::TokenKind::RawIdent => IDENT,
+            rustc_lexer::TokenKind::Literal { kind, .. } => return from_rustc_literal(kind),
+
+            rustc_lexer::TokenKind::Lifetime { starts_with_number } => {
+                if *starts_with_number {
+                    err = "Lifetime name cannot start with a number";
+                }
+                LIFETIME_IDENT
+            }
+
+            rustc_lexer::TokenKind::Semi => T![;],
+            rustc_lexer::TokenKind::Comma => T![,],
+            rustc_lexer::TokenKind::Dot => T![.],
+            rustc_lexer::TokenKind::OpenParen => T!['('],
+            rustc_lexer::TokenKind::CloseParen => T![')'],
+            rustc_lexer::TokenKind::OpenBrace => T!['{'],
+            rustc_lexer::TokenKind::CloseBrace => T!['}'],
+            rustc_lexer::TokenKind::OpenBracket => T!['['],
+            rustc_lexer::TokenKind::CloseBracket => T![']'],
+            rustc_lexer::TokenKind::At => T![@],
+            rustc_lexer::TokenKind::Pound => T![#],
+            rustc_lexer::TokenKind::Tilde => T![~],
+            rustc_lexer::TokenKind::Question => T![?],
+            rustc_lexer::TokenKind::Colon => T![:],
+            rustc_lexer::TokenKind::Dollar => T![$],
+            rustc_lexer::TokenKind::Eq => T![=],
+            rustc_lexer::TokenKind::Bang => T![!],
+            rustc_lexer::TokenKind::Lt => T![<],
+            rustc_lexer::TokenKind::Gt => T![>],
+            rustc_lexer::TokenKind::Minus => T![-],
+            rustc_lexer::TokenKind::And => T![&],
+            rustc_lexer::TokenKind::Or => T![|],
+            rustc_lexer::TokenKind::Plus => T![+],
+            rustc_lexer::TokenKind::Star => T![*],
+            rustc_lexer::TokenKind::Slash => T![/],
+            rustc_lexer::TokenKind::Caret => T![^],
+            rustc_lexer::TokenKind::Percent => T![%],
+            rustc_lexer::TokenKind::Unknown => ERROR,
+        }
+    };
+
+    let err = if err.is_empty() { None } else { Some(err) };
+    (syntax_kind, err)
+}
+
+fn from_rustc_literal(kind: &rustc_lexer::LiteralKind) -> (SyntaxKind, Option<&'static str>) {
+    let mut err = "";
+
+    let syntax_kind = match *kind {
+        rustc_lexer::LiteralKind::Int { empty_int, base: _ } => {
+            if empty_int {
+                err = "Missing digits after the integer base prefix";
+            }
+            INT_NUMBER
+        }
+        rustc_lexer::LiteralKind::Float { empty_exponent, base: _ } => {
+            if empty_exponent {
+                err = "Missing digits after the exponent symbol";
+            }
+            FLOAT_NUMBER
+        }
+        rustc_lexer::LiteralKind::Char { terminated } => {
+            if !terminated {
+                err = "Missing trailing `'` symbol to terminate the character literal";
+            }
+            CHAR
+        }
+        rustc_lexer::LiteralKind::Byte { terminated } => {
+            if !terminated {
+                err = "Missing trailing `'` symbol to terminate the byte literal";
+            }
+            BYTE
+        }
+        rustc_lexer::LiteralKind::Str { terminated } => {
+            if !terminated {
+                err = "Missing trailing `\"` symbol to terminate the string literal";
+            }
+            STRING
+        }
+        rustc_lexer::LiteralKind::ByteStr { terminated } => {
+            if !terminated {
+                err = "Missing trailing `\"` symbol to terminate the byte string literal";
+            }
+            BYTE_STRING
+        }
+        rustc_lexer::LiteralKind::RawStr { err: raw_str_err, .. } => {
+            if let Some(raw_str_err) = raw_str_err {
+                err = match raw_str_err {
+                    rustc_lexer::RawStrError::InvalidStarter { .. } => "Missing `\"` symbol after `#` symbols to begin the raw string literal",
+                    rustc_lexer::RawStrError::NoTerminator { expected, found, .. } => if expected == found {
+                        "Missing trailing `\"` to terminate the raw string literal"
+                    } else {
+                        "Missing trailing `\"` with `#` symbols to terminate the raw string literal"
+                    },
+                    rustc_lexer::RawStrError::TooManyDelimiters { .. } => "Too many `#` symbols: raw strings may be delimited by up to 65535 `#` symbols",
+                };
+            };
+            STRING
+        }
+        rustc_lexer::LiteralKind::RawByteStr { err: raw_str_err, .. } => {
+            if let Some(raw_str_err) = raw_str_err {
+                err = match raw_str_err {
+                    rustc_lexer::RawStrError::InvalidStarter { .. } => "Missing `\"` symbol after `#` symbols to begin the raw byte string literal",
+                    rustc_lexer::RawStrError::NoTerminator { expected, found, .. } => if expected == found {
+                        "Missing trailing `\"` to terminate the raw byte string literal"
+                    } else {
+                        "Missing trailing `\"` with `#` symbols to terminate the raw byte string literal"
+                    },
+                    rustc_lexer::RawStrError::TooManyDelimiters { .. } => "Too many `#` symbols: raw byte strings may be delimited by up to 65535 `#` symbols",
+                };
+            };
+
+            BYTE_STRING
+        }
+    };
+
+    let err = if err.is_empty() { None } else { Some(err) };
+    (syntax_kind, err)
+}

crates/parser/src/lib.rs

@@ -18,6 +18,7 @@
 //! [`Parser`]: crate::parser::Parser
 #![allow(rustdoc::private_intra_doc_links)]
 
+mod lexer_token;
 mod token_set;
 mod syntax_kind;
 mod event;
@@ -25,9 +26,12 @@ mod parser;
 mod grammar;
 mod tokens;
 
+#[cfg(test)]
+mod tests;
+
 pub(crate) use token_set::TokenSet;
 
-pub use crate::{syntax_kind::SyntaxKind, tokens::Tokens};
+pub use crate::{lexer_token::LexerToken, syntax_kind::SyntaxKind, tokens::Tokens};
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct ParseError(pub Box<String>);

crates/parser/src/tests.rs

@@ -0,0 +1,68 @@
+use std::{
+    fmt::Write,
+    fs,
+    path::{Path, PathBuf},
+};
+
+use expect_test::expect_file;
+
+use crate::LexerToken;
+
+#[test]
+fn valid_lexes_input() {
+    for case in TestCase::list("lexer/ok") {
+        let actual = lex(&case.text);
+        expect_file![case.txt].assert_eq(&actual)
+    }
+}
+
+#[test]
+fn invalid_lexes_input() {
+    for case in TestCase::list("lexer/err") {
+        let actual = lex(&case.text);
+        expect_file![case.txt].assert_eq(&actual)
+    }
+}
+
+fn lex(text: &str) -> String {
+    let mut res = String::new();
+    let mut offset = 0;
+    for token in LexerToken::tokenize(text) {
+        let token_text = &text[offset..][..token.len];
+        offset += token.len;
+        let err = token.error.map(|err| format!(" error: {}", err)).unwrap_or_default();
+        writeln!(res, "{:?} {:?}{}", token.kind, token_text, err).unwrap();
+    }
+    res
+}
+
+#[derive(PartialEq, Eq, PartialOrd, Ord)]
+struct TestCase {
+    rs: PathBuf,
+    txt: PathBuf,
+    text: String,
+}
+
+impl TestCase {
+    fn list(path: &'static str) -> Vec<TestCase> {
+        let crate_root_dir = Path::new(env!("CARGO_MANIFEST_DIR"));
+        let test_data_dir = crate_root_dir.join("test_data");
+        let dir = test_data_dir.join(path);
+
+        let mut res = Vec::new();
+        let read_dir = fs::read_dir(&dir)
+            .unwrap_or_else(|err| panic!("can't `read_dir` {}: {}", dir.display(), err));
+        for file in read_dir {
+            let file = file.unwrap();
+            let path = file.path();
+            if path.extension().unwrap_or_default() == "rs" {
+                let rs = path;
+                let txt = rs.with_extension("txt");
+                let text = fs::read_to_string(&rs).unwrap();
+                res.push(TestCase { rs, txt, text });
+            }
+        }
+        res.sort();
+        res
+    }
+}