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

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

Index: pkg/analyzer/lib/dart/element/element.dart
diff --git a/pkg/analyzer/lib/dart/element/element.dart b/pkg/analyzer/lib/dart/element/element.dart
index 5edb586cc8b29f1b47beb881125e4c7e4496b3e5..f7dbe75406e424889f0c82e910fe07f98a27997a 100644
--- a/pkg/analyzer/lib/dart/element/element.dart
+++ b/pkg/analyzer/lib/dart/element/element.dart
@@ -1574,6 +1574,15 @@ abstract class MethodElement implements ClassMemberElement, ExecutableElement {
 
   @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);
 }
 
 /**