Helper ast node sequences must not wrongly grab ownership of the enclosing

runtime/vm/code_generator_ia32.cc

 // Copyright (c) 2011, 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/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/code_generator.h"
 
 #include "lib/error.h"
@@ skipping 870 matching lines @@
   GenerateCallRuntime(node->id(),
       node->token_index(), kCloneContextRuntimeEntry);
   __ popl(EAX);
   __ popl(CTX);  // result: cloned context. Set as current context.
 }
 
 
 void CodeGenerator::VisitSequenceNode(SequenceNode* node_sequence) {
   CodeGeneratorState codegen_state(this);
   LocalScope* scope = node_sequence->scope();
-  ASSERT(scope != NULL);
-  intptr_t num_context_variables = scope->num_context_variables();
+  const intptr_t num_context_variables =
+      (scope != NULL) ? scope->num_context_variables() : 0;
   if (num_context_variables > 0) {
     // The loop local scope declares variables that are captured.
     // Allocate and chain a new context.
     __ movl(EDX, Immediate(num_context_variables));
     const ExternalLabel label("alloc_context",
                               StubCode::AllocateContextEntryPoint());
     GenerateCall(node_sequence->token_index(), &label);
 
     // Chain the new context in EAX to its parent in CTX.
     __ movl(FieldAddress(EAX, Context::parent_offset()), CTX);
@@ skipping 1840 matching lines @@
                         message_buffer, kMessageBufferSize,
                         format, args);
   va_end(args);
   Isolate::Current()->long_jump_base()->Jump(1, message_buffer);
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32