gccrs: Ensure uniqueness on Path probe's

When we lookup names in paths such as Foo::bar, foo is a type we resolve
and then we lookup 'bar' based on what type Foo is which includes probing
relevant bounds of this type. We currently return a vector of possible
candidates and this patch changes it so that we return a set of unique
items based on DefId.

Addresses #1555

gcc/rust/ChangeLog:

	* backend/rust-compile-expr.cc
	(CompileExpr::resolve_method_address): Use auto and minor change
	in candidate init.
	* typecheck/rust-hir-type-check-path.cc
	(TypeCheckExpr::resolve_segments): Likewise.
	* typecheck/rust-hir-type-check-type.cc: Likewise.
	* backend/rust-compile-resolve-path.cc
	(HIRCompileBase::query_compile): Likewise. Removecall to
	set_ty_ref.
	* typecheck/rust-hir-path-probe.h (struct PathProbeCandidate): Add
	locus initializer in ctor, implement get_defid.
	(class PathProbeType::Probe): return a set instead of vector.
	Adjust class impl.
	(class ReportMultipleCandidateError): Do not inherit from
	HIRImplVisitor anymore and remove corresponding impl. Adjust for
	change in Probe. Simplify Report handling.
	(class PathProbeImplTrait::Probe): Adjust return type.

2 files changed, 6 insertions, 6 deletions

diff --git a/gcc/rust/backend/rust-compile-expr.cc b/gcc/rust/backend/rust-compile-expr.cc
index d58e225..ddf914f 100644
--- a/gcc/rust/backend/rust-compile-expr.cc
+++ b/gcc/rust/backend/rust-compile-expr.cc
@@ -1982,7 +1982,7 @@ CompileExpr::resolve_method_address (TyTy::FnType *fntype, HirId ref,
   // trait-impl-item's definition
 
   auto root = receiver->get_root ();
-  std::vector<Resolver::PathProbeCandidate> candidates
+  auto candidates
     = Resolver::PathProbeType::Probe (root, segment, true /* probe_impls */,
 				      false /* probe_bounds */,
 				      true /* ignore_mandatory_trait_items */);
@@ -2011,7 +2011,7 @@ CompileExpr::resolve_method_address (TyTy::FnType *fntype, HirId ref,
       // implementation and we should just return error_mark_node
 
       rust_assert (candidates.size () == 1);
-      auto &candidate = candidates.at (0);
+      auto &candidate = *candidates.begin ();
       rust_assert (candidate.is_impl_candidate ());
       rust_assert (candidate.ty->get_kind () == TyTy::TypeKind::FNDEF);
       TyTy::FnType *candidate_call = static_cast<TyTy::FnType *> (candidate.ty);
diff --git a/gcc/rust/backend/rust-compile-resolve-path.cc b/gcc/rust/backend/rust-compile-resolve-path.cc
index 2cc9505..ab8e628 100644
--- a/gcc/rust/backend/rust-compile-resolve-path.cc
+++ b/gcc/rust/backend/rust-compile-resolve-path.cc
@@ -251,7 +251,7 @@ HIRCompileBase::query_compile (HirId ref, TyTy::BaseType *lookup,
 	  // item so its up to us to figure out if this path should resolve
 	  // to an trait-impl-block-item or if it can be defaulted to the
 	  // trait-impl-item's definition
-	  std::vector<Resolver::PathProbeCandidate> candidates
+	  auto candidates
 	    = Resolver::PathProbeImplTrait::Probe (receiver, final_segment,
 						   trait_ref);
 	  if (candidates.size () == 0)
@@ -270,7 +270,9 @@ HIRCompileBase::query_compile (HirId ref, TyTy::BaseType *lookup,
 	    }
 	  else
 	    {
-	      Resolver::PathProbeCandidate &candidate = candidates.at (0);
+	      rust_assert (candidates.size () == 1);
+
+	      auto candidate = *candidates.begin ();
 	      rust_assert (candidate.is_impl_candidate ());
 
 	      HIR::ImplBlock *impl = candidate.item.impl.parent;
@@ -288,8 +290,6 @@ HIRCompileBase::query_compile (HirId ref, TyTy::BaseType *lookup,
 	      else
 		return CompileInherentImplItem::Compile (impl_item, ctx, lookup,
 							 true, expr_locus);
-
-	      lookup->set_ty_ref (impl_item->get_impl_mappings ().get_hirid ());
 	    }
 	}
     }