MalformedType used for all invalid type annotations.

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 f10d3d72408a924c2bf51196010434ddaa2dc7e6..53a395d2dcee76464f35a97f1c8e71bf8bca28ec 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
@@ -961,6 +961,10 @@ throwRuntimeError(message) {
   throw new RuntimeError(message);
 }
 
+throwMalformedSubtypeError(value, type, reasons) {

[ngeoffray, 2012/11/30 12:00:40]

Why this helper and not inlining it line 1511?

[Johnni Winther, 2012/12/04 10:07:17]

The builder will generate calls for it.

+  throw new TypeErrorImplementation.malformedSubtype(value, type, reasons);
+}
+
 throwAbstractClassInstantiationError(className) {
   throw new AbstractClassInstantiationError(className);
 }
@@ -1502,6 +1506,11 @@ voidTypeCheck(value) {
   throw new TypeErrorImplementation(value, 'void');
 }
 
+malformedTypeCheck(value, type, reasons) {
+  if (value == null) return value;
+  throwMalformedSubtypeError(value, type, reasons);
+}
+
 /**
  * Special interface recognized by the compiler and implemented by DOM
  * objects that support integer indexing. This interface is not
@@ -1516,9 +1525,22 @@ abstract class JavaScriptIndexingBehavior {
 /** Thrown by type assertions that fail. */
 class TypeErrorImplementation implements TypeError {
   final String message;
+
+  /**
+   * Normal type error caused by a failed subtype test.
+   */
   TypeErrorImplementation(Object value, String type)
-    : message = "type '${Primitives.objectTypeName(value)}' is not a subtype "
-                "of type '$type'";
+      : message = "type '${Primitives.objectTypeName(value)}' is not a subtype "
+                  "of type '$type'";
+
+  /**
+   * Type error caused by a subtype test on a malformed type.
+   */
+  TypeErrorImplementation.malformedSubtype(Object value,
+                                           String type, String reasons)
+      : message = "type '${Primitives.objectTypeName(value)}' is not a subtype "
+                  "of type '$type' because '$type' is malformed: $reasons.";
+
   String toString() => message;
 }