Throw a runtime error when trying to call a constructor of a class that could not be resolved.

lib/compiler/implementation/lib/js_helper.dart

Index: lib/compiler/implementation/lib/js_helper.dart
diff --git a/lib/compiler/implementation/lib/js_helper.dart b/lib/compiler/implementation/lib/js_helper.dart
index b969c9d4e621241ded0e0b8e6ca8b7b19023fd1e..e685ab1e46ce1d338531cbfb51869db2a83842df 100644
--- a/lib/compiler/implementation/lib/js_helper.dart
+++ b/lib/compiler/implementation/lib/js_helper.dart
@@ -764,16 +764,28 @@ makeLiteralListConst(list) {
   return list;
 }
 
+throwRuntimeError(message) {
+  var error = JS('var', @'new Error(#)', message);
+  JS('void', @'#.isDartRuntimeError = true', error);
+  JS('var', 'throw #', error);
+}
+
 /**
  * Called from catch blocks in generated code to extract the Dart
  * exception from the thrown value. The thrown value may have been
- * created by [captureStackTrace] or it may be a 'native' JS
- * exception.
+ * created by [captureStackTrace],  it may be a 'native' JS
+ * exception or it may be a Dart runtime error which is uncatchable.

[ngeoffray, 2012/08/24 15:43:48]

Please check with the specification if that's the intent.

[karlklose, 2012/08/28 09:09:15]

Done, changed it to a normal throw.

  *
  * Some native exceptions are mapped to new Dart instances, others are
  * returned unmodified.
  */
 unwrapException(ex) {
+  // Check if this exception is a Dart runtime error. Runtime errors cannot
+  // be caught by generated code.
+  if (JS('bool', @'"isDartRuntimeError" in #', ex)) {
+    JS('void', @'throw #', ex);
+  }
+
   // Note that we are checking if the object has the property. If it
   // has, it could be set to null if the thrown value is null.
   if (JS('bool', @'"dartException" in #', ex)) {