From 943b42f7433a15abfbe6ec718281012d690e5fd8 Mon Sep 17 00:00:00 2001 From: Nathaniel McCallum Date: Sun, 10 Aug 2025 01:38:17 -0400 Subject: [PATCH] parser: fix parsing of trait bound polarity and for-binders MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The rustc AST allows both `for<>` binders and `?` polarity modifiers in trait bounds, but they are parsed in a specific order and validated for correctness: 1. `for<>` binder is parsed first. 2. Polarity modifiers (`?`, `!`) are parsed second. 3. The parser validates that binders and polarity modifiers do not conflict: ```rust if let Some(binder_span) = binder_span { match modifiers.polarity { BoundPolarity::Maybe(polarity_span) => { // Error: "for<...> binder not allowed with ? polarity" } } } ``` This implies: - `for<> ?Sized` → Valid syntax. Invalid semantics. - `?for<> Sized` → Invalid syntax. However, rust-analyzer incorrectly had special-case logic that allowed `?for<>` as valid syntax. This fix removes that incorrect special case, making rust-analyzer reject `?for<> Sized` as a syntax error, matching rustc behavior. This has caused confusion in other crates (such as syn) which rely on these files to implement correct syntax evaluation. --- crates/parser/src/grammar/generic_params.rs | 11 ++--- crates/parser/test_data/generated/runner.rs | 6 +++ ...invalid_question_for_type_trait_bound.rast | 49 +++++++++++++++++++ .../invalid_question_for_type_trait_bound.rs | 1 + .../ok/question_for_type_trait_bound.rast | 23 +++++---- .../ok/question_for_type_trait_bound.rs | 2 +- 6 files changed, 73 insertions(+), 19 deletions(-) create mode 100644 crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rast create mode 100644 crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rs diff --git a/crates/parser/src/grammar/generic_params.rs b/crates/parser/src/grammar/generic_params.rs index cb1b59f64977..d419817e5cd7 100644 --- a/crates/parser/src/grammar/generic_params.rs +++ b/crates/parser/src/grammar/generic_params.rs @@ -182,12 +182,6 @@ fn type_bound(p: &mut Parser<'_>) -> bool { ); m.complete(p, USE_BOUND_GENERIC_ARGS); } - T![?] if p.nth_at(1, T![for]) => { - // test question_for_type_trait_bound - // fn f() where T: ?for<> Sized {} - p.bump_any(); - types::for_type(p, false) - } _ => { if path_type_bound(p).is_err() { m.abandon(p); @@ -219,8 +213,13 @@ fn path_type_bound(p: &mut Parser<'_>) -> Result<(), ()> { // test async_trait_bound // fn async_foo(_: impl async Fn(&i32)) {} p.eat(T![async]); + // test question_for_type_trait_bound + // fn f() where T: for<> ?Sized {} p.eat(T![?]); + // test_err invalid_question_for_type_trait_bound + // fn f() where T: ?for<> Sized {} + if paths::is_use_path_start(p) { types::path_type_bounds(p, false); // test_err type_bounds_macro_call_recovery diff --git a/crates/parser/test_data/generated/runner.rs b/crates/parser/test_data/generated/runner.rs index c642e1a3354f..a3cfe64e6e73 100644 --- a/crates/parser/test_data/generated/runner.rs +++ b/crates/parser/test_data/generated/runner.rs @@ -796,6 +796,12 @@ mod err { #[test] fn impl_type() { run_and_expect_errors("test_data/parser/inline/err/impl_type.rs"); } #[test] + fn invalid_question_for_type_trait_bound() { + run_and_expect_errors( + "test_data/parser/inline/err/invalid_question_for_type_trait_bound.rs", + ); + } + #[test] fn let_else_right_curly_brace() { run_and_expect_errors("test_data/parser/inline/err/let_else_right_curly_brace.rs"); } diff --git a/crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rast b/crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rast new file mode 100644 index 000000000000..b060ee81d617 --- /dev/null +++ b/crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rast @@ -0,0 +1,49 @@ +SOURCE_FILE + FN + FN_KW "fn" + WHITESPACE " " + NAME + IDENT "f" + GENERIC_PARAM_LIST + L_ANGLE "<" + TYPE_PARAM + NAME + IDENT "T" + R_ANGLE ">" + PARAM_LIST + L_PAREN "(" + R_PAREN ")" + WHITESPACE " " + WHERE_CLAUSE + WHERE_KW "where" + WHITESPACE " " + WHERE_PRED + PATH_TYPE + PATH + PATH_SEGMENT + NAME_REF + IDENT "T" + COLON ":" + WHITESPACE " " + TYPE_BOUND_LIST + QUESTION "?" + WHERE_PRED + FOR_BINDER + FOR_KW "for" + GENERIC_PARAM_LIST + L_ANGLE "<" + R_ANGLE ">" + WHITESPACE " " + PATH_TYPE + PATH + PATH_SEGMENT + NAME_REF + IDENT "Sized" + WHITESPACE " " + BLOCK_EXPR + STMT_LIST + L_CURLY "{" + R_CURLY "}" + WHITESPACE "\n" +error 20: expected comma +error 31: expected colon diff --git a/crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rs b/crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rs new file mode 100644 index 000000000000..f80dd90d446c --- /dev/null +++ b/crates/parser/test_data/parser/inline/err/invalid_question_for_type_trait_bound.rs @@ -0,0 +1 @@ +fn f() where T: ?for<> Sized {} diff --git a/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rast b/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rast index cb296153c8f1..69db1aee2c5a 100644 --- a/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rast +++ b/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rast @@ -27,19 +27,18 @@ SOURCE_FILE WHITESPACE " " TYPE_BOUND_LIST TYPE_BOUND + FOR_BINDER + FOR_KW "for" + GENERIC_PARAM_LIST + L_ANGLE "<" + R_ANGLE ">" + WHITESPACE " " QUESTION "?" - FOR_TYPE - FOR_BINDER - FOR_KW "for" - GENERIC_PARAM_LIST - L_ANGLE "<" - R_ANGLE ">" - WHITESPACE " " - PATH_TYPE - PATH - PATH_SEGMENT - NAME_REF - IDENT "Sized" + PATH_TYPE + PATH + PATH_SEGMENT + NAME_REF + IDENT "Sized" WHITESPACE " " BLOCK_EXPR STMT_LIST diff --git a/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rs b/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rs index f80dd90d446c..96353df3b9b3 100644 --- a/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rs +++ b/crates/parser/test_data/parser/inline/ok/question_for_type_trait_bound.rs @@ -1 +1 @@ -fn f() where T: ?for<> Sized {} +fn f() where T: for<> ?Sized {}