gccrs: add diagnostic for E0229 no associated type arguments allowed here

It seems bounds in qualified paths are not allowed to specify associated
type bindings because its going to be associated with the impl block
anyway.

Fixes #2369

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-base.h: add flag
	* typecheck/rust-hir-type-check-type.cc (TypeCheckType::visit): likewise
	* typecheck/rust-tyty-bounds.cc: new diagnostic

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2369.rs: New test.

Signed-off-by: Philip Herron <[email protected]>

Author: philberty

gcc/rust/typecheck/rust-hir-type-check-base.h

@@ -40,7 +40,8 @@ class TypeCheckBase
   TyTy::TypeBoundPredicate get_predicate_from_bound (
     HIR::TypePath &path,
     tl::optional<std::reference_wrapper<HIR::Type>> associated_self,
-    BoundPolarity polarity = BoundPolarity::RegularBound);
+    BoundPolarity polarity = BoundPolarity::RegularBound,
+    bool is_qualified_type = false);
 
   bool check_for_unconstrained (
     const std::vector<TyTy::SubstitutionParamMapping> &params_to_constrain,

gcc/rust/typecheck/rust-hir-type-check-type.cc

@@ -193,8 +193,10 @@ TypeCheckType::visit (HIR::QualifiedPathInType &path)
     return;
 
   // get the predicate for the bound
-  auto specified_bound = get_predicate_from_bound (qual_path_type.get_trait (),
-						   qual_path_type.get_type ());
+  auto specified_bound
+    = get_predicate_from_bound (qual_path_type.get_trait (),
+				qual_path_type.get_type (),
+				BoundPolarity::RegularBound, true);
   if (specified_bound.is_error ())
     return;
 

gcc/rust/typecheck/rust-tyty-bounds.cc

@@ -196,7 +196,7 @@ TyTy::TypeBoundPredicate
 TypeCheckBase::get_predicate_from_bound (
   HIR::TypePath &type_path,
   tl::optional<std::reference_wrapper<HIR::Type>> associated_self,
-  BoundPolarity polarity)
+  BoundPolarity polarity, bool is_qualified_type_path)
 {
   TyTy::TypeBoundPredicate lookup = TyTy::TypeBoundPredicate::error ();
   bool already_resolved
@@ -222,6 +222,21 @@ TypeCheckBase::get_predicate_from_bound (
 	if (final_generic_seg.has_generic_args ())
 	  {
 	    args = final_generic_seg.get_generic_args ();
+	    if (args.get_binding_args ().size () > 0
+		&& associated_self.has_value () && is_qualified_type_path)
+	      {
+		auto &binding_args = args.get_binding_args ();
+
+		rich_location r (line_table, args.get_locus ());
+		for (auto it = binding_args.begin (); it != binding_args.end ();
+		     it++)
+		  {
+		    auto &arg = *it;
+		    r.add_fixit_remove (arg.get_locus ());
+		  }
+		rust_error_at (r, ErrorCode::E0229,
+			       "associated type bindings are not allowed here");
+	      }
 	  }
       }
       break;

gcc/testsuite/rust/compile/issue-2369.rs

@@ -0,0 +1,21 @@
+#[lang = "sized"]
+trait Sized {}
+
+fn main() {
+    pub trait Foo {
+        type A;
+        fn boo(&self) -> <Self as Foo>::A;
+    }
+
+    struct Bar;
+
+    impl Foo for isize {
+        type A = usize;
+        fn boo(&self) -> usize {
+            42
+        }
+    }
+
+    fn baz<I>(x: &<I as Foo<A = Bar>>::A) {}
+    // { dg-error "associated type bindings are not allowed here .E0229." "" { target *-*-* } .-1 }
+}