Use "Object" as the reified type of covariant override parameters.

pkg/analyzer/lib/dart/element/element.dart

 // Copyright (c) 2014, 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.
 
 /**
  * Defines the element model. The element model describes the semantic (as
  * opposed to syntactic) structure of Dart code. The syntactic structure of the
  * code is modeled by the [AST structure](../ast/ast.dart).
  *
  * The element model consists of two closely related kinds of objects: elements
@@ skipping 1556 matching lines @@
  * Clients may not extend, implement or mix-in this class.
  */
 abstract class MethodElement implements ClassMemberElement, ExecutableElement {
   /**
    * An empty list of method elements.
    */
   static const List<MethodElement> EMPTY_LIST = const <MethodElement>[];
 
   @override
   MethodDeclaration computeNode();
+
+  /**
+   * Gets the reified type of a tear-off of this method.
+   *
+   * If any of the parameters in the method are covariant, they are replaced
+   * with Object in the returned type. If no covariant parameters are present,
+   * returns `this`.
+   */
+  FunctionType getReifiedType(DartType objectType);
 }
 
 /**
  * A pseudo-element that represents multiple elements defined within a single
  * scope that have the same name. This situation is not allowed by the language,
  * so objects implementing this interface always represent an error. As a
  * result, most of the normal operations on elements do not make sense and will
  * return useless results.
  *
  * Clients may not extend, implement or mix-in this class.
@@ skipping 449 matching lines @@
   DartType get type;
 
   /**
    * Return a representation of the value of this variable, forcing the value
    * to be computed if it had not previously been computed, or `null` if either
    * this variable was not declared with the 'const' modifier or if the value of
    * this variable could not be computed because of errors.
    */
   DartObject computeConstantValue();
 }