remove covariant generics option

lib/src/checker/rules.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.
 
 library dev_compiler.src.checker.rules;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 
@@ skipping 279 matching lines @@
       List<DartType> tArgs1 = i1.typeArguments;
       List<DartType> tArgs2 = i2.typeArguments;
 
       // TODO(leafp): Verify that this is always true
       // Do raw types get filled in?
       assert(tArgs1.length == tArgs2.length);
 
       for (int i = 0; i < tArgs1.length; i++) {
         DartType t1 = tArgs1[i];
         DartType t2 = tArgs2[i];
-        if (options.covariantGenerics) {
-          if (!isSubTypeOf(t1, t2)) return false;
-        } else {
-          if ((t1 != t2) && !t2.isDynamic) return false;
-        }
+        if (!isSubTypeOf(t1, t2)) return false;
       }
       return true;
     }
 
     if (i2.isDartCoreFunction) {
       if (i1.element.getMethod("call") != null) return true;
     }
 
     if (i1 == provider.objectType) return false;
 
@@ skipping 471 matching lines @@
     var entries = e.entries;
     bool inferEntry(MapLiteralEntry entry) {
       return _inferExpression(entry.key, kType, errors) &&
           _inferExpression(entry.value, vType, errors);
     }
     var b = entries.every(inferEntry);
     if (b) annotateMapLiteral(e, targs);
     return b;
   }
 }