gccrs: Resolve lang item types

Lang items might not already be resolved when an expression depending on
them is resolved.

The new test is a copy of for-loop1.rs in the same directory, but the
main function item is moved towards the top of the file. It still
produces a compiler error after type checking, but that can be resolved
in another patch.

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-expr.cc
	(TypeCheckExpr::visit (BoxExpr)): Attempt to resolve lang item,
	instead of just looking it up.
	(TypeCheckExpr::visit (RangeFromToExpr)): Likewise.
	(TypeCheckExpr::visit (RangeFromExpr)): Likewise.
	(TypeCheckExpr::visit (RangeToExpr)): Likewise.
	(TypeCheckExpr::visit (RangeFullExpr)): Likewise.

gcc/testsuite/ChangeLog:

	* rust/compile/for-loop3.rs: New test.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>

Author: powerboat9

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

@@ -197,11 +197,8 @@ TypeCheckExpr::visit (HIR::BoxExpr &expr)
     = mappings.get_lang_item (LangItem::Kind::OWNED_BOX, expr.get_locus ());
 
   HIR::Item *item = mappings.lookup_defid (owned_box_defid).value ();
-  TyTy::BaseType *item_type = nullptr;
+  TyTy::BaseType *item_type = TypeCheckItem::Resolve (*item);
 
-  bool ok
-    = context->lookup_type (item->get_mappings ().get_hirid (), &item_type);
-  rust_assert (ok);
   if (item_type->get_kind () != TyTy::TypeKind::ADT)
     {
       rust_error_at (item->get_locus (), ErrorCode::E0718,
@@ -829,10 +826,7 @@ TypeCheckExpr::visit (HIR::RangeFromToExpr &expr)
   // look it up and it _must_ be a struct definition
   HIR::Item *item = mappings.lookup_defid (respective_lang_item_id).value ();
 
-  TyTy::BaseType *item_type = nullptr;
-  bool ok
-    = context->lookup_type (item->get_mappings ().get_hirid (), &item_type);
-  rust_assert (ok);
+  TyTy::BaseType *item_type = TypeCheckItem::Resolve (*item);
   rust_assert (item_type->get_kind () == TyTy::TypeKind::ADT);
   TyTy::ADTType *adt = static_cast<TyTy::ADTType *> (item_type);
 
@@ -880,10 +874,7 @@ TypeCheckExpr::visit (HIR::RangeFromExpr &expr)
   // look it up and it _must_ be a struct definition
   HIR::Item *item = mappings.lookup_defid (respective_lang_item_id).value ();
 
-  TyTy::BaseType *item_type = nullptr;
-  bool ok
-    = context->lookup_type (item->get_mappings ().get_hirid (), &item_type);
-  rust_assert (ok);
+  TyTy::BaseType *item_type = TypeCheckItem::Resolve (*item);
   rust_assert (item_type->get_kind () == TyTy::TypeKind::ADT);
   TyTy::ADTType *adt = static_cast<TyTy::ADTType *> (item_type);
 
@@ -924,10 +915,7 @@ TypeCheckExpr::visit (HIR::RangeToExpr &expr)
   // look it up and it _must_ be a struct definition
   HIR::Item *item = mappings.lookup_defid (respective_lang_item_id).value ();
 
-  TyTy::BaseType *item_type = nullptr;
-  bool ok
-    = context->lookup_type (item->get_mappings ().get_hirid (), &item_type);
-  rust_assert (ok);
+  TyTy::BaseType *item_type = TypeCheckItem::Resolve (*item);
   rust_assert (item_type->get_kind () == TyTy::TypeKind::ADT);
   TyTy::ADTType *adt = static_cast<TyTy::ADTType *> (item_type);
 
@@ -1065,10 +1053,7 @@ TypeCheckExpr::visit (HIR::RangeFullExpr &expr)
   // look it up and it _must_ be a struct definition
   HIR::Item *item = mappings.lookup_defid (respective_lang_item_id).value ();
 
-  TyTy::BaseType *item_type = nullptr;
-  bool ok
-    = context->lookup_type (item->get_mappings ().get_hirid (), &item_type);
-  rust_assert (ok);
+  TyTy::BaseType *item_type = TypeCheckItem::Resolve (*item);
   rust_assert (item_type->is_unit ());
 
   infered = item_type;