Simplify runtime type support.

sdk/lib/_internal/compiler/implementation/lib/js_helper.dart

Index: sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart b/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
index 6dae54a419aa7bc9389316cf0fd57520654e820c..0cf9c4f1a1f43b62449a1ed769d09487dc5d8477 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
@@ -1131,8 +1131,6 @@ getRuntimeTypeInfo(target) {
   var res = JS('var', r'#.builtin$typeInfo', target);
   // If the object does not have runtime type information, return an
   // empty literal, to avoid null checks.
-  // TODO(ngeoffray): Make the object a top-level field to avoid
-  // allocating a new object every single time.

[ngeoffray, 2012/11/15 08:58:09]

Why removing this?

[karlklose, 2012/11/16 13:37:19]

That was an accident. Restored.

   return (res == null) ? JS('var', '{}') : res;
 }
 
@@ -1479,7 +1477,25 @@ Type getOrCreateCachedRuntimeType(String key) {
   return result;
 }
 
+String getClassName(var object) {
+  return JS('String', r'#.constructor.builtin$cls', object);
+}
+
 String getRuntimeTypeString(var object) {
+  String className = isJsArray(object) ? 'List' : getClassName(object);
   var typeInfo = JS('Object', r'#.builtin$typeInfo', object);

[ngeoffray, 2012/11/15 08:58:09]

'Object' -> 'var'. I know this is not documented, but it will conflict with
Stephen's work.

[karlklose, 2012/11/16 13:37:19]

Done.

-  return JS('String', r'#.runtimeType', typeInfo);
+  if (typeInfo == null) return className;
+  StringBuffer arguments = new StringBuffer();
+  int length = JS('int', r'#.length', typeInfo);

[ngeoffray, 2012/11/15 08:58:09]

Looks to me that you don't really need all these JS. builtin$typeInfo is an
array.

[karlklose, 2012/11/16 13:37:19]

Done.

+  for (var i = 0; i < length; i++) {
+    if (i > 0) {
+      arguments.add(', ');
+    }
+    var argument = JS('String', r'#[#]', typeInfo, i);

[ngeoffray, 2012/11/15 08:58:09]

typeInfo[i]

[karlklose, 2012/11/16 13:37:19]

Done.

+    if (JS('bool', r'# == (void 0)', argument)) {

[ngeoffray, 2012/11/15 08:58:09]

argument == null

[karlklose, 2012/11/16 13:37:19]

Done.

+      argument = 'dynamic';
+    }
+    arguments.add(argument != null ? argument : 'dynamic');

[ngeoffray, 2012/11/15 08:58:09]

This is weird. builtin$typeInfo should have one kind of null in its entries.

[karlklose, 2012/11/16 13:37:19]

This was a merge conflict, removed.

+  }
+  return '$className<$arguments>';
 }