Bring type variables into static scope, but produce compile-time error when they are used.

lib/compiler/implementation/typechecker.dart

Index: lib/compiler/implementation/typechecker.dart
diff --git a/lib/compiler/implementation/typechecker.dart b/lib/compiler/implementation/typechecker.dart
index b57c1a8bd0f8be3933349e9172f5b7788187116a..1980fe6fbeb50b1606c53b9e8439c358b64b7338 100644
--- a/lib/compiler/implementation/typechecker.dart
+++ b/lib/compiler/implementation/typechecker.dart
@@ -118,6 +118,20 @@ class VoidType implements DartType {
   String toString() => name.slowToString();
 }
 
+class MalformedType implements DartType {
+  const MalformedType(this.element);
+  SourceString get name => element.name;
+  final MalformedTypeElement element;
+
+  DartType unalias(Compiler compiler) => this;
+
+  int hashCode() => 1733;
+
+  bool operator ==(other) => other is MalformedType;
+
+  String toString() => name.slowToString();
+}
+
 class InterfaceType implements DartType {
   final Element element;
   final Link<DartType> arguments;
@@ -276,6 +290,8 @@ class Types {
 
     if (t is VoidType) {
       return false;
+    } else if (t is MalformedType) {
+      return false;
     } else if (t is InterfaceType) {
       if (s is !InterfaceType) return false;
       ClassElement tc = t.element;