gccrs: fix parser error on parenthesis types

Do not cast parenthesised types to TraitBound types.

Fixes #4148

gcc/rust/ChangeLog:

	* ast/rust-path.cc (TypePath::to_trait_bound): Check if in
	parenthesis.
	* hir/tree/rust-hir-type.cc (ParenthesisedType::to_trait_bound):
	Likewise.
	* hir/tree/rust-hir.cc (TypePath::to_trait_bound): Likewise.

gcc/testsuite/ChangeLog:

	* rust/compile/issue-4148.rs: Test should produce errors.

Signed-off-by: lenny.chiadmi-delage <[email protected]>

Author: Villosse

gcc/rust/ast/rust-path.cc

@@ -290,6 +290,11 @@ TypePath::make_debug_string () const
 TraitBound *
 TypePath::to_trait_bound (bool in_parens) const
 {
+  // If already in parentheses, don't convert to trait bound
+  // This ensures (TypePath) stays as ParenthesisedType in the parser
+  if (in_parens)
+    return nullptr;
+
   return new TraitBound (TypePath (*this), get_locus (), in_parens);
 }
 

gcc/rust/hir/tree/rust-hir-type.cc

@@ -101,8 +101,13 @@ ParenthesisedType::operator= (ParenthesisedType const &other)
 }
 
 std::unique_ptr<TraitBound>
-ParenthesisedType::to_trait_bound (bool in_parens ATTRIBUTE_UNUSED) const
+ParenthesisedType::to_trait_bound (bool in_parens) const
 {
+  /* If already in parentheses, don't convert - should stay as
+   * ParenthesisedType */
+  if (in_parens)
+    return nullptr;
+
   /* NOTE: obviously it is unknown whether the internal type is a trait bound
    * due to polymorphism, so just let the internal type handle it. As
    * parenthesised type, it must be in parentheses. */

gcc/rust/hir/tree/rust-hir.cc

@@ -2798,6 +2798,11 @@ Expr::as_string () const
 std::unique_ptr<TraitBound>
 TypePath::to_trait_bound (bool in_parens) const
 {
+  // If already in parentheses, don't convert to trait bound
+  // This ensures (TypePath) stays as ParenthesisedType in the parser
+  if (in_parens)
+    return nullptr;
+
   // create clone FIXME is this required? or is copy constructor automatically
   // called?
   TypePath copy (*this);

gcc/testsuite/rust/compile/issue-4148.rs

@@ -1,5 +1,3 @@
-// { dg-excess-errors "warnings" }
-
 // TODO: all `xfail` conditions should be changed to `target` once the ICE in #4148 is resolved
 
 pub fn ret_parens(x: i32) -> i32 {