fix #30423, covariant parameter tearoff type should be Object

pkg/analyzer/lib/src/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.
 
 library analyzer.src.dart.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 7207 matching lines @@
   @override
   void appendTo(StringBuffer buffer) {
     buffer.write(displayName);
     super.appendTo(buffer);
   }
 
   @override
   MethodDeclaration computeNode() =>
       getNodeMatching((node) => node is MethodDeclaration);
 
+  // TODO(jmesserly): this implementation is completely wrong:
+  // It does not handle covariant parameters from a generic class.
+  // It drops type parameters from generic methods.
+  // Since this method was for DDC, it should be removed.
   @override
   FunctionType getReifiedType(DartType objectType) {

[Jennifer Messerly, 2017/08/12 00:10:49]

FYI: I want to remove this, because it's broken, and DDC is the only consumer.
However it does appear in the Element API. I doubt anyone uses it, though. Happy
to clean up in a follow up CL.

[Paul Berry, 2017/08/14 16:11:47]

Sounds good!  I suggest you mark it as @deprecated in this CL so that no one
starts using it in the meantime.

     // Check whether we have any covariant parameters.
     // Usually we don't, so we can use the same type.
     bool hasCovariant = false;
     for (ParameterElement parameter in parameters) {
       if (parameter.isCovariant) {
         hasCovariant = true;
         break;
       }
     }
 
@@ skipping 2695 matching lines @@
 
   @override
   DartObject computeConstantValue() => null;
 
   @override
   void visitChildren(ElementVisitor visitor) {
     super.visitChildren(visitor);
     _initializer?.accept(visitor);
   }
 }