Rollup merge of rust-lang#137140 - Noratrieb:const-move, r=jieyouxu,compiler-errors

Fix const items not being allowed to be called `r#move` or `r#static`

Because of an ambiguity with const closures, the parser needs to ensure that for a const item, the `const` keyword isn't followed by a `move` or `static` keyword, as that would indicate a const closure:

```rust
fn main() {
  const move // ...
}
```

This check did not take raw identifiers into account, therefore being unable to distinguish between `const move` and `const r#move`. The latter is obviously not a const closure, so it should be allowed as a const item.

This fixes the check in the parser to only treat `const ...` as a const closure if it's followed by the *proper keyword*, and not a raw identifier.

Additionally, this adds a large test that tests for all raw identifiers in all kinds of positions, including `const`, to prevent issues like this one from occurring again.

fixes rust-lang#137128

Author: matthiaskrgr

compiler/rustc_parse/src/parser/mod.rs

@@ -754,9 +754,9 @@ impl<'a> Parser<'a> {
         self.is_keyword_ahead(0, &[kw::Const])
             && self.look_ahead(1, |t| match &t.kind {
                 // async closures do not work with const closures, so we do not parse that here.
-                token::Ident(kw::Move | kw::Static, _) | token::OrOr | token::BinOp(token::Or) => {
-                    true
-                }
+                token::Ident(kw::Move | kw::Static, IdentIsRaw::No)
+                | token::OrOr
+                | token::BinOp(token::Or) => true,
                 _ => false,
             })
     }

compiler/rustc_span/src/symbol.rs

@@ -104,6 +104,8 @@ symbols! {
         Gen:                "gen", // >= 2024 Edition only
         Try:                "try", // >= 2018 Edition only
 
+        // NOTE: When adding new keywords, consider adding them to the ui/parser/raw/raw-idents.rs test.
+
         // "Lifetime keywords": regular keywords with a leading `'`.
         // Matching predicates: `is_any_keyword`
         UnderscoreLifetime: "'_",

tests/ui/parser/raw/raw-idents.rs

@@ -0,0 +1,158 @@
+//@ check-pass
+//@ revisions:e2015 e2018 e2021 e2024
+//@[e2015] edition:2015
+//@[e2018] edition:2018
+//@[e2021] edition:2021
+//@[e2024] edition:2024
+
+// Ensure that all (usable as identifier) keywords work as raw identifiers in all positions.
+// This was motivated by issue #137128, where `r#move`/`r#static`` did not work as `const` names
+// due to a parser check not acounting for raw identifiers.
+
+#![crate_type = "lib"]
+#![allow(dead_code, nonstandard_style)]
+
+// NOTE: It is vital to only use a `tt` fragment to avoid confusing
+// the parser with nonterminals that can mask bugs.
+
+macro_rules! tests {
+    ($kw:tt) => {
+        mod $kw {
+            mod const_item {
+                const $kw: () = ();
+            }
+            mod static_item {
+                static $kw: () = ();
+            }
+            mod fn_item {
+                fn $kw() {}
+            }
+            mod mod_and_use_item {
+                mod $kw {
+                    use super::$kw;
+                }
+            }
+            mod ty_alias_item {
+                type $kw = ();
+            }
+            mod struct_item {
+                struct $kw { $kw: () }
+            }
+            mod enum_item {
+                enum $kw { $kw }
+            }
+            mod union_item {
+                union $kw { $kw: () }
+            }
+            mod trait_item {
+                trait $kw {
+                    fn $kw() {}
+                }
+            }
+            mod generics_and_impl {
+                struct A<$kw>($kw);
+                enum B<$kw> { A($kw) }
+                trait Tr<$kw> {
+                    type $kw;
+                }
+
+                impl<$kw> Tr<$kw> for A<$kw> {
+                    type $kw = ();
+                }
+                impl<$kw> B<$kw> {}
+            }
+            mod extern_crate {
+                #[cfg(any())]
+                extern crate $kw;
+            }
+            mod body {
+                fn expr() {
+                    let $kw = 0;
+                    let b = $kw;
+                    assert_eq!($kw, b);
+                    type $kw = ();
+                    let $kw: $kw = ();
+                    let _ = $kw as $kw;
+                }
+                fn pat_const() {
+                    const $kw: u8 = 0;
+
+                    // Ensure that $kw actually matches the constant.
+                    #[forbid(unreachable_patterns)]
+                    match 1 {
+                        $kw => {}
+                        _ => {}
+                    }
+                }
+                fn pat_binding() {
+                    match 1 {
+                        $kw => {}
+                        _ => {}
+                    }
+                }
+            }
+        }
+    };
+}
+
+tests!(r#break);
+tests!(r#const);
+tests!(r#continue);
+tests!(r#else);
+tests!(r#enum);
+tests!(r#extern);
+tests!(r#false);
+tests!(r#fn);
+tests!(r#for);
+tests!(r#if);
+tests!(r#impl);
+tests!(r#in);
+tests!(r#let);
+tests!(r#loop);
+tests!(r#match);
+tests!(r#mod);
+tests!(r#move);
+tests!(r#mut);
+tests!(r#pub);
+tests!(r#ref);
+tests!(r#return);
+tests!(r#static);
+tests!(r#struct);
+tests!(r#trait);
+tests!(r#true);
+tests!(r#type);
+tests!(r#unsafe);
+tests!(r#use);
+tests!(r#where);
+tests!(r#while);
+tests!(r#abstract);
+tests!(r#become);
+tests!(r#box);
+tests!(r#do);
+tests!(r#final);
+tests!(r#macro);
+tests!(r#override);
+tests!(r#priv);
+tests!(r#typeof);
+tests!(r#unsized);
+tests!(r#virtual);
+tests!(r#yield);
+tests!(r#async);
+tests!(r#await);
+tests!(r#dyn);
+tests!(r#gen);
+tests!(r#try);
+
+// Weak keywords:
+tests!(auto);
+tests!(builtin);
+tests!(catch);
+tests!(default);
+tests!(macro_rules);
+tests!(raw);
+tests!(reuse);
+tests!(contract_ensures);
+tests!(contract_requires);
+tests!(safe);
+tests!(union);
+tests!(yeet);