Void is not required to be `null` anymore.

runtime/vm/kernel_to_il.cc

 // Copyright (c) 2016, 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 <set>
 
 #include "vm/kernel_to_il.h"
 
 #include "vm/compiler.h"
 #include "vm/intermediate_language.h"
@@ skipping 4035 matching lines @@
   }
   return instructions;
 }
 
 
 Fragment FlowGraphBuilder::CheckAssignableInCheckedMode(
     const AbstractType& dst_type,
     const dart::String& dst_name) {
   Fragment instructions;
   if (I->type_checks() && !dst_type.IsDynamicType() &&
-      !dst_type.IsObjectType()) {
+      !dst_type.IsObjectType() && !dst_type.IsVoidType()) {
     LocalVariable* top_of_stack = MakeTemporary();
     instructions += LoadLocal(top_of_stack);
     instructions += AssertAssignable(dst_type, dst_name);
     instructions += Drop();
   }
   return instructions;
 }
 
 
 Fragment FlowGraphBuilder::AssertBool() {
@@ skipping 2807 matching lines @@
     thread->clear_sticky_error();
     return error.raw();
   }
 }
 
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)