Do not register typechecks against type variables of typedefs.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

 // Copyright (c) 2012, 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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   Selector getGetterSelectorInComplexSendSet(SendSet node);
@@ skipping 1619 matching lines @@
       // When the element is a field, we are actually resolving its
       // initial value, which should not have access to instance
       // fields.
       inInstanceContext = (element.isInstanceMember() && !element.isField())
           || element.isGenerativeConstructor(),
       this.currentClass = element.isMember() ? element.getEnclosingClass()
                                              : null,
       this.statementScope = new StatementScope(),
       typeResolver = new TypeResolver(compiler),
       scope = element.buildScope(),
       inCheckContext = compiler.enableTypeAssertions,

[ngeoffray, 2013/02/28 20:08:42]

If you did inCheckContext = compiler.enableTypeAssertions && !element.isTypedef,
would that work too? Seems like a better place to put the check.

[karlklose, 2013/03/01 08:23:38]

That works, too, using the enclosingElement.

I think it may be hard to find this invariant of the isChecks here, so I left
the assert in the enqueuer.

       inCatchBlock = false,
       super(compiler);
 
   ResolutionEnqueuer get world => compiler.enqueuer.resolution;
 
   Element lookup(Node node, SourceString name) {
     Element result = scope.lookup(name);
     if (!Elements.isUnresolved(result)) {
       if (!inInstanceContext && result.isInstanceMember()) {
         compiler.reportErrorCode(
@@ skipping 89 matching lines @@
         classElement.ensureResolved(compiler);
       }
       return useElement(node, element);
     }
   }
 
   Element visitTypeAnnotation(TypeAnnotation node) {
     DartType type = resolveTypeAnnotation(node);
     if (type != null) {
       if (inCheckContext) {
-        compiler.enqueuer.resolution.registerIsCheck(type);
+        if (!Types.isTypeVariableOfTypedef(type)) {
+          compiler.enqueuer.resolution.registerIsCheck(type);
+        }
       }
       return type.element;
     }
     return null;
   }
 
   Element defineElement(Node node, Element element,
                         {bool doAddToScope: true}) {
     compiler.ensure(element != null);
     mapping[node] = element;
@@ skipping 800 matching lines @@
     }
   }
 
   DartType resolveTypeAnnotation(TypeAnnotation node) {
     Function report = typeRequired ? error : warning;
     DartType type = typeResolver.resolveTypeAnnotation(
         node, scope, enclosingElement,
         onFailure: report, whenResolved: useType);
     if (type == null) return null;
     if (inCheckContext) {
-      compiler.enqueuer.resolution.registerIsCheck(type);
+      if (!Types.isTypeVariableOfTypedef(type)) {
+        compiler.enqueuer.resolution.registerIsCheck(type);
+      }
     }
     if (typeRequired || inCheckContext) {
       if (type is InterfaceType) {
         InterfaceType itf = type;
         itf.typeArguments.forEach((DartType argument) {
           analyzeTypeArgument(type, argument);
         });
       }
       // TODO(ngeoffray): Also handle T a (in checked mode).
     }
@@ skipping 1219 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }