Rollup merge of #143065 - compiler-errors:enum-recovery, r=oli-obk

Improve recovery when users write `where:`

Improve recovery of `where:`.

Fixes https://github.com/rust-lang/rust/issues/143023

The erroneous suggestion was because we were seeing `:` then a type, which the original impl thought must be a struct field. Make this a bit more accurate by checking for a non-reserved ident (which should be a field name).

Also, make a custom parser error for `where:` so we can continue parsing after the colon.

2 files changed, 7 insertions, 5 deletions

diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index 9b4535dcfbc..fc816f2cb79 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/compiler/rustc_ast/src/token.rs
@@ -893,7 +893,7 @@ impl Token {
             || self.is_qpath_start()
             || matches!(self.is_metavar_seq(), Some(MetaVarKind::Path))
             || self.is_path_segment_keyword()
-            || self.is_ident() && !self.is_reserved_ident()
+            || self.is_non_reserved_ident()
     }
 
     /// Returns `true` if the token is a given keyword, `kw`.
@@ -937,6 +937,10 @@ impl Token {
         self.is_non_raw_ident_where(Ident::is_reserved)
     }
 
+    pub fn is_non_reserved_ident(&self) -> bool {
+        self.ident().is_some_and(|(id, raw)| raw == IdentIsRaw::Yes || !Ident::is_reserved(id))
+    }
+
     /// Returns `true` if the token is the identifier `true` or `false`.
     pub fn is_bool_lit(&self) -> bool {
         self.is_non_raw_ident_where(|id| id.name.is_bool_lit())
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index 3c231be20dc..c60185cdde0 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -634,10 +634,8 @@ impl TokenStream {
                     (
                         TokenTree::Token(token_left, Spacing::Alone),
                         TokenTree::Token(token_right, _),
-                    ) if ((token_left.is_ident() && !token_left.is_reserved_ident())
-                        || token_left.is_lit())
-                        && ((token_right.is_ident() && !token_right.is_reserved_ident())
-                            || token_right.is_lit()) =>
+                    ) if (token_left.is_non_reserved_ident() || token_left.is_lit())
+                        && (token_right.is_non_reserved_ident() || token_right.is_lit()) =>
                     {
                         token_left.span
                     }