Fix bad assert in static type propagation.

runtime/vm/intermediate_language.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/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/locations.h"
@@ skipping 490 matching lines @@
 
 RawAbstractType* ClosureCallComp::StaticType() const {
   // The closure is the first argument to the call.
   const AbstractType& function_type =
       AbstractType::Handle(ArgumentAt(0)->StaticType());
   if (function_type.IsDynamicType() || function_type.IsFunctionInterface()) {
     // The function type is not statically known or simply Function.
     return Type::DynamicType();
   }
   const Class& signature_class = Class::Handle(function_type.type_class());
-  ASSERT(signature_class.IsSignatureClass());
   const Function& signature_function =
       Function::Handle(signature_class.signature_function());
+  if (signature_function.IsNull()) {
+    // Attempting to invoke a non-closure object.
+    return Type::DynamicType();
+  }
   // TODO(regis): The result type may be generic. Consider upper bounds.
   return signature_function.result_type();
 }
 
 
 RawAbstractType* InstanceCallComp::StaticType() const {
   return Type::DynamicType();
 }
 
 
@@ skipping 672 matching lines @@
   const ExternalLabel label(closure_function.ToCString(), stub.EntryPoint());
   compiler->GenerateCall(token_index(), try_index(), &label,
                          PcDescriptors::kOther);
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 
 #undef __
 
 }  // namespace dart