check is_ident before parse_ident

compiler/rustc_parse/src/parser/item.rs

@@ -387,8 +387,8 @@ fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
         let span = if is_pub { self.prev_token.span.to(ident_span) } else { ident_span };
         let insert_span = ident_span.shrink_to_lo();
 
-        let ident = if (!is_const
-            || self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Parenthesis)))
+        let ident = if self.token.is_ident()
+            && (!is_const || self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Parenthesis)))
             && self.look_ahead(1, |t| {
                 [
                     token::Lt,

tests/ui/parser/ice-issue-127600.rs

@@ -0,0 +1,2 @@
+const!(&raw mut a);
+//~^ ERROR expected identifier, found `!`

tests/ui/parser/ice-issue-127600.stderr

@@ -0,0 +1,8 @@
+error: expected identifier, found `!`
+  --> $DIR/ice-issue-127600.rs:1:6
+   |
+LL | const!(&raw mut a);
+   |      ^ expected identifier
+
+error: aborting due to 1 previous error
+