Implement type checking of map literals (issue 221).

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 1387 matching lines @@
     __ PushObject(negate_result ? bool_false : bool_true);
     return;
   }
 
   const Immediate raw_null =
       Immediate(reinterpret_cast<intptr_t>(Object::null()));
   Label done;
   // If type is instantiated and non-parameterized, we can inline code
   // checking whether the tested instance is a Smi.
   if (type.IsInstantiated()) {
-    // A null object is not an instance of any type, except of Object, Dynamic,
-    // and Null type.
+    // A null object is only an instance of Object and Dynamic, which has
+    // already been checked above (if the type is instantiated). So we can
+    // return false here if the instance is null (and if the type is
+    // instantiated).
     // We can only inline this null check if the type is instantiated at compile
     // time, since an uninstantiated type at compile time could be Object or
     // Dynamic at run time.
     Label non_null;
     __ cmpl(EAX, raw_null);
     __ j(NOT_EQUAL, &non_null, Assembler::kNearJump);
     __ PushObject(negate_result ? bool_true : bool_false);
     __ jmp(&done, Assembler::kNearJump);
 
     __ Bind(&non_null);
@@ skipping 1339 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