Fix ClassMirror.typeArguments handling for dynamic only type arguments

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/dart_entry.h"
 #include "vm/exceptions.h"
 #include "vm/object_store.h"
@@ skipping 574 matching lines @@
 DEFINE_NATIVE_ENTRY(ClassMirror_type_variables, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(MirrorReference, ref, arguments->NativeArgAt(0));
   const Class& klass = Class::Handle(ref.GetClassReferent());
   return CreateTypeVariableList(klass);
 }
 
 
 DEFINE_NATIVE_ENTRY(ClassMirror_type_arguments, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(AbstractType, type, arguments->NativeArgAt(0));
 
-  const AbstractTypeArguments& args =
-      AbstractTypeArguments::Handle(type.arguments());
-  if (args.IsNull()) {
+  const Class& cls = Class::Handle(type.type_class());
+  const intptr_t num_params = cls.NumTypeParameters();
+
+  if (num_params == 0) {
     return Object::empty_array().raw();
   }
 
-  const Class& cls = Class::Handle(type.type_class());
-  const intptr_t num_params = cls.NumTypeParameters();
-  const intptr_t num_inherited_args = args.Length() - num_params;
-
   const Array& result = Array::Handle(Array::New(num_params));
   AbstractType& arg_type = AbstractType::Handle();
   Instance& type_mirror = Instance::Handle();
+  const AbstractTypeArguments& args =
+      AbstractTypeArguments::Handle(type.arguments());
+
+  // Handle argument lists that have been optimized away, because either no
+  // arguments have been provided, or all arguments are dynamic. Return a list
+  // of typemirrors on dynamic in this case.
+  if (args.IsNull()) {
+    arg_type ^= Object::dynamic_type();
+    type_mirror ^= CreateTypeMirror(arg_type);
+    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);
     type_mirror = CreateTypeMirror(arg_type);
     result.SetAt(i, type_mirror);
   }
   return result.raw();
 }
 
 
 DEFINE_NATIVE_ENTRY(TypeVariableMirror_owner, 1) {
@@ skipping 658 matching lines @@
 }
 
 
 DEFINE_NATIVE_ENTRY(VariableMirror_type, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(MirrorReference, ref, arguments->NativeArgAt(0));
   const Field& field = Field::Handle(ref.GetFieldReferent());
   return field.type();
 }
 
 }  // namespace dart