cancel a not emitted error after parsing const generic args

Author: TaKO8Ki

compiler/rustc_parse/src/parser/path.rs

@@ -630,10 +630,14 @@ impl<'a> Parser<'a> {
                 Ok(ty) => GenericArg::Type(ty),
                 Err(err) => {
                     if is_const_fn {
-                        if let Ok(expr) = (*snapshot).parse_expr_res(Restrictions::CONST_EXPR, None)
-                        {
-                            self.restore_snapshot(snapshot);
-                            return Ok(Some(self.dummy_const_arg_needs_braces(err, expr.span)));
+                        match (*snapshot).parse_expr_res(Restrictions::CONST_EXPR, None) {
+                            Ok(expr) => {
+                                self.restore_snapshot(snapshot);
+                                return Ok(Some(self.dummy_const_arg_needs_braces(err, expr.span)));
+                            }
+                            Err(err) => {
+                                err.cancel();
+                            }
                         }
                     }
                     // Try to recover from possible `const` arg without braces.

src/test/ui/const-generics/ice-const-generic-function-return-ty.rs

@@ -0,0 +1,5 @@
+// #95163
+fn return_ty() -> impl Into<<() as Reexported;
+//~^ ERROR expected one of `(`, `::`, `<`, or `>`, found `;`
+
+fn main() {}

src/test/ui/const-generics/ice-const-generic-function-return-ty.stderr

@@ -0,0 +1,8 @@
+error: expected one of `(`, `::`, `<`, or `>`, found `;`
+  --> $DIR/ice-const-generic-function-return-ty.rs:2:46
+   |
+LL | fn return_ty() -> impl Into<<() as Reexported;
+   |                                              ^ expected one of `(`, `::`, `<`, or `>`
+
+error: aborting due to previous error
+