[gcc/devel/rust/master] Add new check for contains_associated_types

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:126c7c9d7a2f9023115d6c692dbcf9e981ba2b4a

commit 126c7c9d7a2f9023115d6c692dbcf9e981ba2b4a
Author: Philip Herron <philip.herron@embecosm.com>
Date:   Wed Aug 31 17:07:51 2022 +0100

    Add new check for contains_associated_types
    
    We don't need to setup associated types when a trait does not contain any
    associated types.

Diff:
---
 gcc/rust/typecheck/rust-hir-trait-resolve.cc |  3 +++
 gcc/rust/typecheck/rust-tyty-bounds.cc       | 15 +++++++++++++++
 gcc/rust/typecheck/rust-tyty.h               |  2 ++
 3 files changed, 20 insertions(+)

diff --git a/gcc/rust/typecheck/rust-hir-trait-resolve.cc b/gcc/rust/typecheck/rust-hir-trait-resolve.cc
index 73575859def..146fe26a762 100644
--- a/gcc/rust/typecheck/rust-hir-trait-resolve.cc
+++ b/gcc/rust/typecheck/rust-hir-trait-resolve.cc
@@ -368,6 +368,9 @@ void
 AssociatedImplTrait::setup_associated_types (
   const TyTy::BaseType *self, const TyTy::TypeBoundPredicate &bound)
 {
+  if (!bound.contains_associated_types ())
+    return;
+
   // compute the constrained impl block generic arguments based on self and the
   // higher ranked trait bound
   TyTy::BaseType *receiver = self->clone ();
diff --git a/gcc/rust/typecheck/rust-tyty-bounds.cc b/gcc/rust/typecheck/rust-tyty-bounds.cc
index 7a1562ab544..811d64bd740 100644
--- a/gcc/rust/typecheck/rust-tyty-bounds.cc
+++ b/gcc/rust/typecheck/rust-tyty-bounds.cc
@@ -374,6 +374,21 @@ TypeBoundPredicate::requires_generic_args () const
   return substitutions.size () > 1;
 }
 
+bool
+TypeBoundPredicate::contains_associated_types () const
+{
+  auto trait_ref = get ();
+  for (const auto &trait_item : trait_ref->get_trait_items ())
+    {
+      bool is_associated_type
+	= trait_item.get_trait_item_type ()
+	  == Resolver::TraitItemReference::TraitItemType::TYPE;
+      if (is_associated_type)
+	return true;
+    }
+  return false;
+}
+
 // trait item reference
 
 const Resolver::TraitItemReference *
diff --git a/gcc/rust/typecheck/rust-tyty.h b/gcc/rust/typecheck/rust-tyty.h
index a351932e432..649f133edb1 100644
--- a/gcc/rust/typecheck/rust-tyty.h
+++ b/gcc/rust/typecheck/rust-tyty.h
@@ -1057,6 +1057,8 @@ public:
 
   bool requires_generic_args () const;
 
+  bool contains_associated_types () const;
+
 private:
   DefId reference;
   Location locus;