diff options
| -rw-r--r-- | compiler/rustc_parse/src/parser/mod.rs | 56 | ||||
| -rw-r--r-- | compiler/rustc_parse/src/parser/tests.rs | 121 |
2 files changed, 147 insertions, 30 deletions
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs index 45ca267fe5d..ef9b3aabc61 100644 --- a/compiler/rustc_parse/src/parser/mod.rs +++ b/compiler/rustc_parse/src/parser/mod.rs @@ -1118,41 +1118,37 @@ impl<'a> Parser<'a> { return looker(&self.token); } - if let Some(&(_, span, _, delim)) = self.token_cursor.stack.last() - && delim != Delimiter::Invisible - { - // We are not in the outermost token stream, and the token stream - // we are in has non-skipped delimiters. Look for skipped - // delimiters in the lookahead range. - let tree_cursor = &self.token_cursor.tree_cursor; - let all_normal = (0..dist).all(|i| { - let token = tree_cursor.look_ahead(i); - !matches!(token, Some(TokenTree::Delimited(.., Delimiter::Invisible, _))) - }); - if all_normal { - // There were no skipped delimiters. Do lookahead by plain indexing. - return match tree_cursor.look_ahead(dist - 1) { - Some(tree) => { - // Indexing stayed within the current token stream. - match tree { - TokenTree::Token(token, _) => looker(token), - TokenTree::Delimited(dspan, _, delim, _) => { - looker(&Token::new(token::OpenDelim(*delim), dspan.open)) - } + // Typically around 98% of the `dist > 0` cases have `dist == 1`, so we + // have a fast special case for that. + if dist == 1 { + // The index is zero because the tree cursor's index always points + // to the next token to be gotten. + match self.token_cursor.tree_cursor.look_ahead(0) { + Some(tree) => { + // Indexing stayed within the current token tree. + return match tree { + TokenTree::Token(token, _) => looker(token), + TokenTree::Delimited(dspan, _, delim, _) => { + looker(&Token::new(token::OpenDelim(*delim), dspan.open)) } + }; + } + None => { + // The tree cursor lookahead went (one) past the end of the + // current token tree. Try to return a close delimiter. + if let Some(&(_, span, _, delim)) = self.token_cursor.stack.last() + && delim != Delimiter::Invisible + { + // We are not in the outermost token stream, so we have + // delimiters. Also, those delimiters are not skipped. + return looker(&Token::new(token::CloseDelim(delim), span.close)); } - None => { - // Indexing went past the end of the current token - // stream. Use the close delimiter, no matter how far - // ahead `dist` went. - looker(&Token::new(token::CloseDelim(delim), span.close)) - } - }; + } } } - // We are in a more complex case. Just clone the token cursor and use - // `next`, skipping delimiters as necessary. Slow but simple. + // Just clone the token cursor and use `next`, skipping delimiters as + // necessary. Slow but simple. let mut cursor = self.token_cursor.clone(); let mut i = 0; let mut token = Token::dummy(); diff --git a/compiler/rustc_parse/src/parser/tests.rs b/compiler/rustc_parse/src/parser/tests.rs index 42392ad2163..5b2d119e42b 100644 --- a/compiler/rustc_parse/src/parser/tests.rs +++ b/compiler/rustc_parse/src/parser/tests.rs @@ -1376,6 +1376,127 @@ fn ttdelim_span() { }); } +// Uses a macro rather than a function so that failure messages mention the +// correct line in the test function. +macro_rules! look { + ($p:ident, $dist:literal, $kind:expr) => { + $p.look_ahead($dist, |tok| assert_eq!($kind, tok.kind)); + }; +} + +#[test] +fn look_ahead() { + create_default_session_globals_then(|| { + let sym_f = Symbol::intern("f"); + let sym_x = Symbol::intern("x"); + #[allow(non_snake_case)] + let sym_S = Symbol::intern("S"); + let raw_no = IdentIsRaw::No; + + let psess = psess(); + let mut p = string_to_parser(&psess, "fn f(x: u32) { x } struct S;".to_string()); + + // Current position is the `fn`. + look!(p, 0, token::Ident(kw::Fn, raw_no)); + look!(p, 1, token::Ident(sym_f, raw_no)); + look!(p, 2, token::OpenDelim(Delimiter::Parenthesis)); + look!(p, 3, token::Ident(sym_x, raw_no)); + look!(p, 4, token::Colon); + look!(p, 5, token::Ident(sym::u32, raw_no)); + look!(p, 6, token::CloseDelim(Delimiter::Parenthesis)); + look!(p, 7, token::OpenDelim(Delimiter::Brace)); + look!(p, 8, token::Ident(sym_x, raw_no)); + look!(p, 9, token::CloseDelim(Delimiter::Brace)); + look!(p, 10, token::Ident(kw::Struct, raw_no)); + look!(p, 11, token::Ident(sym_S, raw_no)); + look!(p, 12, token::Semi); + // Any lookahead past the end of the token stream returns `Eof`. + look!(p, 13, token::Eof); + look!(p, 14, token::Eof); + look!(p, 15, token::Eof); + look!(p, 100, token::Eof); + + // Move forward to the first `x`. + for _ in 0..3 { + p.bump(); + } + look!(p, 0, token::Ident(sym_x, raw_no)); + look!(p, 1, token::Colon); + look!(p, 2, token::Ident(sym::u32, raw_no)); + look!(p, 3, token::CloseDelim(Delimiter::Parenthesis)); + look!(p, 4, token::OpenDelim(Delimiter::Brace)); + look!(p, 5, token::Ident(sym_x, raw_no)); + look!(p, 6, token::CloseDelim(Delimiter::Brace)); + look!(p, 7, token::Ident(kw::Struct, raw_no)); + look!(p, 8, token::Ident(sym_S, raw_no)); + look!(p, 9, token::Semi); + look!(p, 10, token::Eof); + look!(p, 11, token::Eof); + look!(p, 100, token::Eof); + + // Move forward to the `;`. + for _ in 0..9 { + p.bump(); + } + look!(p, 0, token::Semi); + // Any lookahead past the end of the token stream returns `Eof`. + look!(p, 1, token::Eof); + look!(p, 100, token::Eof); + + // Move one past the `;`, i.e. past the end of the token stream. + p.bump(); + look!(p, 0, token::Eof); + look!(p, 1, token::Eof); + look!(p, 100, token::Eof); + + // Bumping after Eof is idempotent. + p.bump(); + look!(p, 0, token::Eof); + look!(p, 1, token::Eof); + look!(p, 100, token::Eof); + }); +} + +/// There used to be some buggy behaviour when using `look_ahead` not within +/// the outermost token stream, which this test covers. +#[test] +fn look_ahead_non_outermost_stream() { + create_default_session_globals_then(|| { + let sym_f = Symbol::intern("f"); + let sym_x = Symbol::intern("x"); + #[allow(non_snake_case)] + let sym_S = Symbol::intern("S"); + let raw_no = IdentIsRaw::No; + + let psess = psess(); + let mut p = string_to_parser(&psess, "mod m { fn f(x: u32) { x } struct S; }".to_string()); + + // Move forward to the `fn`, which is not within the outermost token + // stream (because it's inside the `mod { ... }`). + for _ in 0..3 { + p.bump(); + } + look!(p, 0, token::Ident(kw::Fn, raw_no)); + look!(p, 1, token::Ident(sym_f, raw_no)); + look!(p, 2, token::OpenDelim(Delimiter::Parenthesis)); + look!(p, 3, token::Ident(sym_x, raw_no)); + look!(p, 4, token::Colon); + look!(p, 5, token::Ident(sym::u32, raw_no)); + look!(p, 6, token::CloseDelim(Delimiter::Parenthesis)); + look!(p, 7, token::OpenDelim(Delimiter::Brace)); + look!(p, 8, token::Ident(sym_x, raw_no)); + look!(p, 9, token::CloseDelim(Delimiter::Brace)); + look!(p, 10, token::Ident(kw::Struct, raw_no)); + look!(p, 11, token::Ident(sym_S, raw_no)); + look!(p, 12, token::Semi); + look!(p, 13, token::CloseDelim(Delimiter::Brace)); + // Any lookahead past the end of the token stream returns `Eof`. + look!(p, 14, token::Eof); + look!(p, 15, token::Eof); + look!(p, 100, token::Eof); + }); +} + // This tests that when parsing a string (rather than a file) we don't try // and read in a file for a module declaration and just parse a stub. // See `recurse_into_file_modules` in the parser. |