Rollup merge of #151171 - issue-141436, r=davidtwco

Do not recover from `Trait()` if generic list is unterminated

If we encounter `fn foo<T: Trait()`, the recovery logic would it as if `Trait` was intended to use the Fn-like trait syntax, but if we don't know for certain that we've parsed a full trait bound (`fn foo<T: Trait()>`), we bail from the recovery as more likely there could have been a missing closing `>` and the `(` corresponds to the start of the fn parameter list.

Fix rust-lang/rust#141436.

compiler/rustc_ast/src/token.rs

@@ -625,12 +625,12 @@ impl TokenKind {
 }
 
 impl Token {
-    pub fn new(kind: TokenKind, span: Span) -> Self {
+    pub const fn new(kind: TokenKind, span: Span) -> Self {
         Token { kind, span }
     }
 
     /// Some token that will be thrown away later.
-    pub fn dummy() -> Self {
+    pub const fn dummy() -> Self {
         Token::new(TokenKind::Question, DUMMY_SP)
     }