Keep types in signatures of function types properly instantiated as the function

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, 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 "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "lib/stacktrace.h"
@@ skipping 106 matching lines @@
  public:
   explicit CheckFunctionTypesVisitor(Thread* thread)
       : classHandle_(Class::Handle(thread->zone())),
         funcHandle_(Function::Handle(thread->zone())),
         typeHandle_(AbstractType::Handle(thread->zone())) {}
 
   void VisitObject(RawObject* obj) {
     if (obj->IsFunction()) {
       funcHandle_ ^= obj;
       classHandle_ ^= funcHandle_.Owner();
+      // Signature functions get created, but not canonicalized, when function
+      // types get instantiated during run time type tests.
+      if (funcHandle_.IsSignatureFunction()) {
+        return;
+      }
       // Verify that the result type of a function is canonical or a
       // TypeParameter.
       typeHandle_ ^= funcHandle_.result_type();
       ASSERT(typeHandle_.IsMalformed() || !typeHandle_.IsResolved() ||
              typeHandle_.IsTypeParameter() || typeHandle_.IsCanonical());
       // Verify that the types in the function signature are all canonical or
       // a TypeParameter.
       const intptr_t num_parameters = funcHandle_.NumParameters();
       for (intptr_t i = 0; i < num_parameters; i++) {
         typeHandle_ = funcHandle_.ParameterTypeAt(i);
@@ skipping 6695 matching lines @@
 }
 
 
 DART_EXPORT void Dart_DumpNativeStackTrace(void* context) {
 #ifndef PRODUCT
   Profiler::DumpStackTrace(context);
 #endif
 }
 
 }  // namespace dart