Fix issue 18646.

runtime/vm/object.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 "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 13820 matching lines @@
   if (raw_ptr()->type_state_ == RawType::kFinalizedInstantiated) {
     return true;
   }
   if (raw_ptr()->type_state_ == RawType::kFinalizedUninstantiated) {
     return false;
   }
   if (arguments() == TypeArguments::null()) {
     return true;
   }
   const TypeArguments& args = TypeArguments::Handle(arguments());
-  const intptr_t num_type_args = args.Length();
+  intptr_t num_type_args = args.Length();
   intptr_t len = num_type_args;  // Check the full vector of type args.
   ASSERT(num_type_args > 0);
   // This type is not instantiated if it refers to type parameters.
   // This IsInstantiated() call may be invoked on an unresolved signature type.
   // Although this type may still be unresolved, the type parameters it may
   // refer to are resolved by definition. We can therefore return the correct
   // result even for an unresolved type. We just need to look at all type
   // arguments and not just at the type parameters.
   if (HasResolvedTypeClass()) {
     const Class& cls = Class::Handle(type_class());
+    len = cls.NumTypeArguments();
+    ASSERT(num_type_args >= len);  // The vector may be longer than necessary.
+    num_type_args = len;
     len = cls.NumTypeParameters();  // Check the type parameters only.
-    ASSERT(num_type_args == cls.NumTypeArguments());
   }
   return (len == 0) || args.IsSubvectorInstantiated(num_type_args - len, len);
 }
 
 
 RawAbstractType* Type::InstantiateFrom(
     const TypeArguments& instantiator_type_arguments,
     Error* bound_error,
     GrowableObjectArray* trail) const {
   ASSERT(IsFinalized() || IsBeingFinalized());
@@ skipping 4990 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart