Use a trail instead of a mark bit when processing recursive types in the VM

runtime/lib/mirrors.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "lib/invocation_mirror.h"
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/exceptions.h"
@@ skipping 299 matching lines @@
     }
     lookup_cls = lookup_cls.SuperClass();
   } while (!lookup_cls.IsNull());
   return Function::null();
 }
 
 static RawInstance* CreateClassMirror(const Class& cls,
                                       const AbstractType& type,
                                       const Bool& is_declaration,
                                       const Instance& owner_mirror) {
+  if (type.IsTypeRef()) {
+    AbstractType& ref_type = AbstractType::Handle(TypeRef::Cast(type).type());
+    ASSERT(!ref_type.IsTypeRef());
+    ASSERT(ref_type.IsCanonical());
+    return CreateClassMirror(cls, ref_type, is_declaration, owner_mirror);
+  }
   ASSERT(!cls.IsDynamicClass() && !cls.IsVoidClass());
   ASSERT(!type.IsNull());
   ASSERT(type.IsFinalized());
-  ASSERT(!type.IsTypeRef());
 
   if (cls.IsSignatureClass()) {
     if (cls.IsCanonicalSignatureClass()) {
       // We represent function types as canonical signature classes.
       return CreateFunctionTypeMirror(cls, type);
     } else {
       // We represent typedefs as non-canonical signature classes.
       return CreateTypedefMirror(cls, type, is_declaration, owner_mirror);
     }
   }
@@ skipping 24 matching lines @@
   String& str = String::Handle();
   str = lib.name();
   args.SetAt(1, str);
   str = lib.url();
   args.SetAt(2, str);
   return CreateMirror(Symbols::_LocalLibraryMirror(), args);
 }
 
 
 static RawInstance* CreateTypeMirror(const AbstractType& type) {
+  if (type.IsTypeRef()) {
+    AbstractType& ref_type = AbstractType::Handle(TypeRef::Cast(type).type());
+    ASSERT(!ref_type.IsTypeRef());
+    ASSERT(ref_type.IsCanonical());
+    return CreateTypeMirror(ref_type);
+  }
   ASSERT(type.IsFinalized());
   ASSERT(!type.IsMalformed());
-  ASSERT(!type.IsTypeRef());
   if (type.HasResolvedTypeClass()) {
     const Class& cls = Class::Handle(type.type_class());
     // Handle void and dynamic types.
     if (cls.IsVoidClass()) {
       Array& args = Array::Handle(Array::New(1));
       args.SetAt(0, Symbols::Void());
       // TODO(mlippautz): Create once in the VM isolate and retrieve from there.
       return CreateMirror(Symbols::_SpecialTypeMirror(), args);
     } else if (cls.IsDynamicClass()) {
       Array& args = Array::Handle(Array::New(1));
@@ skipping 872 matching lines @@
     for (intptr_t i = 0; i < num_params; i++) {
       result.SetAt(i, type_mirror);
     }
     return result.raw();
   }
 
   ASSERT(args.Length() >= num_params);
   const intptr_t num_inherited_args = args.Length() - num_params;
   for (intptr_t i = 0; i < num_params; i++) {
     arg_type ^= args.TypeAt(i + num_inherited_args);
-    arg_type = arg_type.Canonicalize();  // Necessary for recursive types.
     type_mirror = CreateTypeMirror(arg_type);
     result.SetAt(i, type_mirror);
   }
   return result.raw();
 }
 
 
 DEFINE_NATIVE_ENTRY(TypeVariableMirror_owner, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(TypeParameter, param, arguments->NativeArgAt(0));
   const Class& owner = Class::Handle(param.parameterized_class());
@@ skipping 772 matching lines @@
 
 DEFINE_NATIVE_ENTRY(VariableMirror_type, 2) {
   GET_NON_NULL_NATIVE_ARGUMENT(MirrorReference, ref, arguments->NativeArgAt(0));
   const Field& field = Field::Handle(ref.GetFieldReferent());
   GET_NATIVE_ARGUMENT(AbstractType, instantiator, arguments->NativeArgAt(1));
   const AbstractType& type = AbstractType::Handle(field.type());
   return InstantiateType(type, instantiator);
 }
 
 }  // namespace dart