gccrs: Change return type of lookup_hir_trait_item

Change the return type to an optional instead of returning a null
pointer. This allows easier tracking of rogue null pointers in the
map. This commit also fixes a bug in trait associated function mangling,
the function was using an already invalidated pointer.

gcc/rust/ChangeLog:

	* backend/rust-compile-resolve-path.cc (HIRCompileBase::query_compile):
	Adapt return type to new optional.
	* backend/rust-mangle-v0.cc (v0_function_path): Change prototype to use
	the generic arguments vector instead of the whole HIR function.
	(v0_path): Fix a bug with a null pointer being used to create the
	trait function mangling.
	* util/rust-hir-map.cc (Mappings::insert_hir_trait_item): Adapt code
	to new return type.
	(Mappings::lookup_hir_trait_item): Change the return type of the
	function to an optional.
	* util/rust-hir-map.h: Update the function's prototype.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

4 files changed, 25 insertions, 20 deletions

diff --git a/gcc/rust/backend/rust-compile-resolve-path.cc b/gcc/rust/backend/rust-compile-resolve-path.cc
index 1f7dc7d..bf294e4 100644
--- a/gcc/rust/backend/rust-compile-resolve-path.cc
+++ b/gcc/rust/backend/rust-compile-resolve-path.cc
@@ -256,10 +256,11 @@ HIRCompileBase::query_compile (HirId ref, TyTy::BaseType *lookup,
       else
 	{
 	  // it might be resolved to a trait item
-	  HIR::TraitItem *trait_item
+	  tl::optional<HIR::TraitItem *> trait_item
 	    = ctx->get_mappings ().lookup_hir_trait_item (ref);
+
 	  HIR::Trait *trait = ctx->get_mappings ().lookup_trait_item_mapping (
-	    trait_item->get_mappings ().get_hirid ());
+	    trait_item.value ()->get_mappings ().get_hirid ());
 
 	  Resolver::TraitReference *trait_ref
 	    = &Resolver::TraitReference::error_node ();
@@ -285,7 +286,7 @@ HIRCompileBase::query_compile (HirId ref, TyTy::BaseType *lookup,
 	      // this means we are defaulting back to the trait_item if
 	      // possible
 	      Resolver::TraitItemReference *trait_item_ref = nullptr;
-	      bool ok = trait_ref->lookup_hir_trait_item (*trait_item,
+	      bool ok = trait_ref->lookup_hir_trait_item (*trait_item.value (),
 							  &trait_item_ref);
 	      rust_assert (ok);				    // found
 	      rust_assert (trait_item_ref->is_optional ()); // has definition
diff --git a/gcc/rust/backend/rust-mangle-v0.cc b/gcc/rust/backend/rust-mangle-v0.cc
index 9be7b2d..0b6d945 100644
--- a/gcc/rust/backend/rust-mangle-v0.cc
+++ b/gcc/rust/backend/rust-mangle-v0.cc
@@ -279,16 +279,17 @@ v0_type_path (V0Path path, std::string ident)
 }
 
 static V0Path
-v0_function_path (V0Path path, Rust::Compile::Context *ctx,
-		  const TyTy::BaseType *ty, HIR::Function *fn,
-		  std::string ident)
+v0_function_path (
+  V0Path path, Rust::Compile::Context *ctx, const TyTy::BaseType *ty,
+  const std::vector<std::unique_ptr<HIR::GenericParam>> &generic_params,
+  std::string ident)
 {
   V0Path v0path;
   v0path.prefix = "N";
   v0path.ns = "v";
   v0path.path = path.as_string ();
   v0path.ident = ident;
-  if (!fn->get_generic_params ().empty ())
+  if (!generic_params.empty ())
     {
       v0path.generic_prefix = "I";
       v0path.generic_postfix = v0_generic_args (ctx, ty) + "E";
@@ -386,7 +387,6 @@ v0_path (Rust::Compile::Context *ctx, const TyTy::BaseType *ty,
     HirId parent_impl_id = UNKNOWN_HIRID;
     HIR::ImplItem *impl_item
       = mappings.lookup_hir_implitem (hir_id, &parent_impl_id);
-    HIR::TraitItem *trait_item = mappings.lookup_hir_trait_item (hir_id);
     HIR::Expr *expr = mappings.lookup_hir_expr (hir_id);
 
     if (impl_item != nullptr)
@@ -395,8 +395,9 @@ v0_path (Rust::Compile::Context *ctx, const TyTy::BaseType *ty,
 	  {
 	    case HIR::ImplItem::FUNCTION: {
 	      HIR::Function *fn = static_cast<HIR::Function *> (impl_item);
-	      v0path = v0_function_path (v0path, ctx, ty, fn,
-					 v0_identifier (seg.get ()));
+	      v0path
+		= v0_function_path (v0path, ctx, ty, fn->get_generic_params (),
+				    v0_identifier (seg.get ()));
 	    }
 	    break;
 	  case HIR::ImplItem::CONSTANT:
@@ -408,13 +409,15 @@ v0_path (Rust::Compile::Context *ctx, const TyTy::BaseType *ty,
 	    break;
 	  }
       }
-    else if (trait_item != nullptr)
+    else if (auto trait_item = mappings.lookup_hir_trait_item (hir_id))
       {
-	switch (trait_item->get_item_kind ())
+	switch (trait_item.value ()->get_item_kind ())
 	  {
 	    case HIR::TraitItem::FUNC: {
-	      HIR::Function *fn = static_cast<HIR::Function *> (impl_item);
-	      v0path = v0_function_path (v0path, ctx, ty, fn,
+	      auto fn = static_cast<HIR::TraitItemFunc *> (*trait_item);
+	      rust_unreachable ();
+	      v0path = v0_function_path (v0path, ctx, ty,
+					 fn->get_decl ().get_generic_params (),
 					 v0_identifier (seg.get ()));
 	    }
 	    break;
@@ -432,8 +435,9 @@ v0_path (Rust::Compile::Context *ctx, const TyTy::BaseType *ty,
 	{
 	  case HIR::Item::ItemKind::Function: {
 	    HIR::Function *fn = static_cast<HIR::Function *> (*item);
-	    v0path = v0_function_path (v0path, ctx, ty, fn,
-				       v0_identifier (seg.get ()));
+	    v0path
+	      = v0_function_path (v0path, ctx, ty, fn->get_generic_params (),
+				  v0_identifier (seg.get ()));
 	  }
 	  break;
 	case HIR::Item::ItemKind::Module:
diff --git a/gcc/rust/util/rust-hir-map.cc b/gcc/rust/util/rust-hir-map.cc
index 535353b..0d134bf 100644
--- a/gcc/rust/util/rust-hir-map.cc
+++ b/gcc/rust/util/rust-hir-map.cc
@@ -406,18 +406,18 @@ void
 Mappings::insert_hir_trait_item (HIR::TraitItem *item)
 {
   auto id = item->get_mappings ().get_hirid ();
-  rust_assert (lookup_hir_trait_item (id) == nullptr);
+  rust_assert (!lookup_hir_trait_item (id).has_value ());
 
   hirTraitItemMappings[id] = item;
   insert_node_to_hir (item->get_mappings ().get_nodeid (), id);
 }
 
-HIR::TraitItem *
+tl::optional<HIR::TraitItem *>
 Mappings::lookup_hir_trait_item (HirId id)
 {
   auto it = hirTraitItemMappings.find (id);
   if (it == hirTraitItemMappings.end ())
-    return nullptr;
+    return tl::nullopt;
 
   return it->second;
 }
diff --git a/gcc/rust/util/rust-hir-map.h b/gcc/rust/util/rust-hir-map.h
index e6df05b..5565ef9 100644
--- a/gcc/rust/util/rust-hir-map.h
+++ b/gcc/rust/util/rust-hir-map.h
@@ -121,7 +121,7 @@ public:
   std::pair<HIR::Enum *, HIR::EnumItem *> lookup_hir_enumitem (HirId id);
 
   void insert_hir_trait_item (HIR::TraitItem *item);
-  HIR::TraitItem *lookup_hir_trait_item (HirId id);
+  tl::optional<HIR::TraitItem *> lookup_hir_trait_item (HirId id);
 
   void insert_hir_extern_block (HIR::ExternBlock *block);
   HIR::ExternBlock *lookup_hir_extern_block (HirId id);