restrict generic function type subtyping

pkg/analyzer/lib/src/task/strong/checker.dart

 // Copyright (c) 2015, 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.
 
 // TODO(jmesserly): this was ported from package:dev_compiler, and needs to be
 // refactored to fit into analyzer.
 library analyzer.src.task.strong.checker;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 1416 matching lines @@
         _checker._recordMessage(
             errorLocation, StrongModeCode.INVALID_FIELD_OVERRIDE, [
           element.enclosingElement.name,
           element.name,
           subType,
           type,
           baseType
         ]);
       }
     }
-    FunctionType concreteSubType = subType;
-    FunctionType concreteBaseType = baseType;
-    if (concreteSubType.typeFormals.isNotEmpty) {
-      if (concreteBaseType.typeFormals.isEmpty) {
-        concreteSubType = rules.instantiateToBounds(concreteSubType);
-      }
-    }
-
-    if (!rules.isOverrideSubtypeOf(concreteSubType, concreteBaseType)) {
+    if (!rules.isOverrideSubtypeOf(subType, baseType)) {
       ErrorCode errorCode;
       if (errorLocation is ExtendsClause) {
         errorCode = StrongModeCode.INVALID_METHOD_OVERRIDE_FROM_BASE;
       } else if (errorLocation.parent is WithClause) {
         errorCode = StrongModeCode.INVALID_METHOD_OVERRIDE_FROM_MIXIN;
       } else {
         errorCode = StrongModeCode.INVALID_METHOD_OVERRIDE;
       }
 
       _checker._recordMessage(errorLocation, errorCode, [
@@ skipping 40 matching lines @@
     var visited = new Set<InterfaceType>();
     do {
       visited.add(current);
       current.mixins.reversed.forEach(
           (m) => _checkIndividualOverridesFromClass(node, m, seen, true));
       _checkIndividualOverridesFromClass(node, current.superclass, seen, true);
       current = current.superclass;
     } while (!current.isObject && !visited.contains(current));
   }
 }