Cleanup interfaces for associated impl mappings

This changes the lookups to return boolean if they are found rather than
default UNKNOWN_HIRID which is more ambigious.

3 files changed, 30 insertions, 21 deletions

diff --git a/gcc/rust/backend/rust-compile-resolve-path.cc b/gcc/rust/backend/rust-compile-resolve-path.cc
index 98c04df..9e8236c 100644
--- a/gcc/rust/backend/rust-compile-resolve-path.cc
+++ b/gcc/rust/backend/rust-compile-resolve-path.cc
@@ -197,11 +197,11 @@ ResolvePathRef::query_compile (HirId ref, TyTy::BaseType *lookup,
 
 	      Analysis::NodeMapping trait_mappings
 		= trait_item_ref->get_parent_trait_mappings ();
-	      auto associated_impl_id
-		= ctx->get_tyctx ()->lookup_associated_impl_mapping_for_self (
-		  trait_mappings.get_hirid (), receiver);
 
-	      rust_assert (associated_impl_id != UNKNOWN_HIRID);
+	      HirId associated_impl_id;
+	      ok = ctx->get_tyctx ()->lookup_associated_impl_mapping_for_self (
+		trait_mappings.get_hirid (), receiver, &associated_impl_id);
+	      rust_assert (ok);
 
 	      Resolver::AssociatedImplTrait *associated = nullptr;
 	      bool found_associated_trait_impl
diff --git a/gcc/rust/typecheck/rust-hir-type-check.h b/gcc/rust/typecheck/rust-hir-type-check.h
index bcad5db..d3dc4c9 100644
--- a/gcc/rust/typecheck/rust-hir-type-check.h
+++ b/gcc/rust/typecheck/rust-hir-type-check.h
@@ -144,16 +144,24 @@ public:
 
   void clear_associated_type_mapping (HirId id)
   {
-    associated_type_mappings[id] = UNKNOWN_HIRID;
+    auto it = associated_type_mappings.find (id);
+    rust_assert (it != associated_type_mappings.end ());
+    associated_type_mappings.erase (it);
   }
 
-  HirId lookup_associated_type_mapping (HirId id, HirId default_value)
+  // lookup any associated type mappings, the out parameter of mapping is
+  // allowed to be nullptr which allows this interface to do a simple does exist
+  // check
+  bool lookup_associated_type_mapping (HirId id, HirId *mapping)
   {
     auto it = associated_type_mappings.find (id);
     if (it == associated_type_mappings.end ())
-      return default_value;
+      return false;
+
+    if (mapping != nullptr)
+      *mapping = it->second;
 
-    return it->second;
+    return true;
   }
 
   void insert_associated_impl_mapping (HirId trait_id,
@@ -169,19 +177,23 @@ public:
     associated_traits_to_impls[trait_id].push_back ({impl_type, impl_id});
   }
 
-  HirId lookup_associated_impl_mapping_for_self (HirId trait_id,
-						 const TyTy::BaseType *self)
+  bool lookup_associated_impl_mapping_for_self (HirId trait_id,
+						const TyTy::BaseType *self,
+						HirId *mapping)
   {
     auto it = associated_traits_to_impls.find (trait_id);
     if (it == associated_traits_to_impls.end ())
-      return UNKNOWN_HIRID;
+      return false;
 
     for (auto &item : it->second)
       {
 	if (item.first->can_eq (self, false))
-	  return item.second;
+	  {
+	    *mapping = item.second;
+	    return true;
+	  }
       }
-    return UNKNOWN_HIRID;
+    return false;
   }
 
   void insert_autoderef_mappings (HirId id,
diff --git a/gcc/rust/typecheck/rust-tyty.cc b/gcc/rust/typecheck/rust-tyty.cc
index b6d88ee..232799b 100644
--- a/gcc/rust/typecheck/rust-tyty.cc
+++ b/gcc/rust/typecheck/rust-tyty.cc
@@ -2198,9 +2198,7 @@ bool
 PlaceholderType::can_resolve () const
 {
   auto context = Resolver::TypeCheckContext::get ();
-  HirId val
-    = context->lookup_associated_type_mapping (get_ty_ref (), UNKNOWN_HIRID);
-  return val != UNKNOWN_HIRID;
+  return context->lookup_associated_type_mapping (get_ty_ref (), nullptr);
 }
 
 BaseType *
@@ -2208,12 +2206,11 @@ PlaceholderType::resolve () const
 {
   auto context = Resolver::TypeCheckContext::get ();
 
-  rust_assert (can_resolve ());
-  HirId val
-    = context->lookup_associated_type_mapping (get_ty_ref (), UNKNOWN_HIRID);
-  rust_assert (val != UNKNOWN_HIRID);
+  HirId mapping;
+  bool ok = context->lookup_associated_type_mapping (get_ty_ref (), &mapping);
+  rust_assert (ok);
 
-  return TyVar (val).get_tyty ();
+  return TyVar (mapping).get_tyty ();
 }
 
 bool