Changes dart2js to warn at reified usage of method type variables.

pkg/compiler/lib/src/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.
 
 library dart2js.resolution.members;
 
 import '../common.dart';
 import '../common/names.dart' show Selectors;
 import '../common/resolution.dart' show Feature;
 import '../compiler.dart' show Compiler;
@@ skipping 1103 matching lines @@
       // `e is! T`.
       Node typeNode = notTypeNode.receiver;
       type = resolveTypeAnnotation(typeNode);
       sendStructure = new IsNotStructure(type);
     } else {
       // `e is T`.
       Node typeNode = node.arguments.head;
       type = resolveTypeAnnotation(typeNode);
       sendStructure = new IsStructure(type);
     }
+
+    // GENERIC_METHODS: Method type variables are not reified so we must warn
+    // about the error which will occur at runtime.
+    if (type is MethodTypeVariableType) {
+      reporter.reportWarningMessage(
+          node, MessageKind.TYPE_VARIABLE_FROM_METHOD_NOT_REIFIED);
+    }
+
     registry.registerTypeUse(new TypeUse.isCheck(type));
     registry.registerSendStructure(node, sendStructure);
     return const NoneResult();
   }
 
   /// Handle a type cast expression, like `a as T`.
   ResolutionResult handleAs(Send node) {
     Node expression = node.receiver;
     visitExpression(expression);
 
     Node typeNode = node.arguments.head;
     DartType type = resolveTypeAnnotation(typeNode);
+
+    // GENERIC_METHODS: Method type variables are not reified so we must warn
+    // about the error which will occur at runtime.
+    if (type is MethodTypeVariableType) {
+      reporter.reportWarningMessage(
+          node, MessageKind.TYPE_VARIABLE_FROM_METHOD_NOT_REIFIED);
+    }
+
     registry.registerTypeUse(new TypeUse.asCast(type));
     registry.registerSendStructure(node, new AsStructure(type));
     return const NoneResult();
   }
 
   /// Handle the unary expression of an unresolved unary operator [text], like
   /// the no longer supported `+a`.
   ResolutionResult handleUnresolvedUnary(Send node, String text) {
     Node expression = node.receiver;
     if (node.isSuperCall) {
@@ skipping 735 matching lines @@
           node,
           name.text,
           MessageKind.TYPE_VARIABLE_WITHIN_STATIC_MEMBER,
           {'typeVariableName': name},
           isError: true);
       registry.registerFeature(Feature.COMPILE_TIME_ERROR);
       semantics = new StaticAccess.invalid(error);
       // TODO(johnniwinther): Clean up registration of elements and selectors
       // for this case.
     } else {
+      // GENERIC_METHODS: Method type variables are not reified so we must warn
+      // about the error which will occur at runtime.
+      if (element.type is MethodTypeVariableType) {
+        reporter.reportWarningMessage(
+            node, MessageKind.TYPE_VARIABLE_FROM_METHOD_NOT_REIFIED);
+      }
       semantics = new StaticAccess.typeParameterTypeLiteral(element);
     }
 
     registry.useElement(node, element);
     registry.registerTypeLiteral(node, element.type);
 
     if (node.isCall) {
       CallStructure callStructure =
           resolveArguments(node.argumentsNode).callStructure;
       Selector selector = callStructure.callSelector;
@@ skipping 2795 matching lines @@
     }
     return const NoneResult();
   }
 }
 
 /// Looks up [name] in [scope] and unwraps the result.
 Element lookupInScope(
     DiagnosticReporter reporter, Node node, Scope scope, String name) {
   return Elements.unwrap(scope.lookup(name), reporter, node);
 }