Rollup merge of #128229 - tdittr:unsafe-extern-abi-error, r=compiler-…

…errors Improve `extern "<abi>" unsafe fn()` error message These errors were already reported in #87217, and fixed by #87235 but missed the case of an explicit ABI. This PR does not cover multiple keywords like `extern "C" pub const unsafe fn()`, but I don't know what a good way to cover this would be. It also seems rarer than `extern "C" unsafe` which I saw happen a few times in workshops.
rust-lang · Jul 26, 2024 · 7eaf747 · 7eaf747
2 parents f9209ae 3fdc991
commit 7eaf747
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Showing 5 changed files with 47 additions and 11 deletions.
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
@@ -2483,12 2483,15 @@ impl<'a> Parser<'a> {
  /// `check_pub` adds additional `pub` to the checks in case users place it
  /// wrongly, can be used to ensure `pub` never comes after `default`.
  pub(super) fn check_fn_front_matter(&mut self, check_pub: bool, case: Case) -> bool {
  const ALL_QUALS: &[Symbol] =
  &[kw::Pub, kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Safe, kw::Extern];
 
  // We use an over-approximation here.
  // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
  // `pub` is added in case users got confused with the ordering like `async pub fn`,
  // only if it wasn't preceded by `default` as `default pub` is invalid.
  let quals: &[Symbol] = if check_pub {
- &[kw::Pub, kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Safe, kw::Extern]
  ALL_QUALS
  } else {
  &[kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Safe, kw::Extern]
  };
@@ -2518,9 2521,9 @@ impl<'a> Parser<'a> {
  || self.check_keyword_case(kw::Extern, case)
  && self.look_ahead(1, |t| t.can_begin_string_literal())
  && (self.look_ahead(2, |t| t.is_keyword_case(kw::Fn, case)) ||
- // this branch is only for better diagnostic in later, `pub` is not allowed here
  // this branch is only for better diagnostics; `pub`, `unsafe`, etc. are not allowed here
  (self.may_recover()
- && self.look_ahead(2, |t| t.is_keyword(kw::Pub))
  && self.look_ahead(2, |t| ALL_QUALS.iter().any(|&kw| t.is_keyword(kw)))
  && self.look_ahead(3, |t| t.is_keyword_case(kw::Fn, case))))
  }
 

diff --git a/tests/ui/parser/issues/issue-19398.rs b/tests/ui/parser/issues/issue-19398.rs
@@ -1,6 1,10 @@
 trait T {
  extern "Rust" unsafe fn foo();
- //~^ ERROR expected `{`, found keyword `unsafe`
  //~^ ERROR expected `fn`, found keyword `unsafe`
  //~| NOTE expected `fn`
  //~| HELP `unsafe` must come before `extern "Rust"`
  //~| SUGGESTION unsafe extern "Rust"
  //~| NOTE keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`
 }
 
 fn main() {}
diff --git a/tests/ui/parser/issues/issue-19398.stderr b/tests/ui/parser/issues/issue-19398.stderr
@@ -1,13 1,13 @@
-error: expected `{`, found keyword `unsafe`
 error: expected `fn`, found keyword `unsafe`
  --> $DIR/issue-19398.rs:2:19
  |
-LL | trait T {
- | - while parsing this item list starting here
 LL | extern "Rust" unsafe fn foo();
- | ^^^^^^ expected `{`
-LL |
-LL | }
- | - the item list ends here
  | --------------^^^^^^
  | | |
  | | expected `fn`
  | help: `unsafe` must come before `extern "Rust"`: `unsafe extern "Rust"`
  |
  = note: keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/parser/issues/issue-87217-keyword-order/wrong-unsafe-abi.rs b/tests/ui/parser/issues/issue-87217-keyword-order/wrong-unsafe-abi.rs
@@ -0,0 1,16 @@
 //@ edition:2018
 
 // There is an order to respect for keywords before a function:
 // `<visibility>, const, async, unsafe, extern, "<ABI>"`
 //
 // This test ensures the compiler is helpful about them being misplaced.
 // Visibilities are tested elsewhere.
 
 extern "C" unsafe fn test() {}
 //~^ ERROR expected `fn`, found keyword `unsafe`
 //~| NOTE expected `fn`
 //~| HELP `unsafe` must come before `extern "C"`
 //~| SUGGESTION unsafe extern "C"
 //~| NOTE keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`
 
 fn main() {}
diff --git a/tests/ui/parser/issues/issue-87217-keyword-order/wrong-unsafe-abi.stderr b/tests/ui/parser/issues/issue-87217-keyword-order/wrong-unsafe-abi.stderr
@@ -0,0 1,13 @@
 error: expected `fn`, found keyword `unsafe`
  --> $DIR/wrong-unsafe-abi.rs:9:12
  |
 LL | extern "C" unsafe fn test() {}
  | -----------^^^^^^
  | | |
  | | expected `fn`
  | help: `unsafe` must come before `extern "C"`: `unsafe extern "C"`
  |
  = note: keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`
 
 error: aborting due to 1 previous error