fix #25578, implement @covariant parameter overrides

pkg/analyzer/lib/src/generated/resolver.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.generated.resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 515 matching lines @@
       }
     }
     return problemReported;
   }
 
   /**
    * Produce a hint if the given [target] could have a value of `null`, and
    * [identifier] is not a name of a getter or a method that exists in the
    * class [Null].
    */
-  void _checkForCanBeNullAfterNullAware(
-      Expression target, Token operator, SimpleIdentifier propertyName, SimpleIdentifier methodName) {
+  void _checkForCanBeNullAfterNullAware(Expression target, Token operator,
+      SimpleIdentifier propertyName, SimpleIdentifier methodName) {
     if (operator?.type == TokenType.QUESTION_PERIOD) {
       return;
     }
     bool isNullTypeMember() {
       if (propertyName != null) {
         String name = propertyName.name;
         return _nullType.lookUpGetter(name, _currentLibrary) != null;
       }
       if (methodName != null) {
         String name = methodName.name;
@@ skipping 6773 matching lines @@
       return;
     }
     FunctionType expectedClosureType = mayByFunctionType as FunctionType;
     // If the expectedClosureType is not more specific than the static type,
     // return.
     DartType staticClosureType = closure.element?.type;
     if (staticClosureType != null &&
         !FunctionTypeImpl.relate(
             expectedClosureType,
             staticClosureType,
-            (DartType t, DartType s) => (t as TypeImpl).isMoreSpecificThan(s),
+            (DartType t, DartType s, _, __) =>
+                (t as TypeImpl).isMoreSpecificThan(s),
             new TypeSystemImpl().instantiateToBounds,
             returnRelation: (s, t) => true)) {
       return;
     }
     // set propagated type for the closure
     closure.propagatedType = expectedClosureType;
     // set inferred types for parameters
     NodeList<FormalParameter> parameters = closure.parameters.parameters;
     List<ParameterElement> expectedParameters = expectedClosureType.parameters;
     for (int i = 0;
@@ skipping 3819 matching lines @@
       return null;
     }
     if (identical(node.staticElement, variable)) {
       if (node.inSetterContext()) {
         result = true;
       }
     }
     return null;
   }
 }