fix #25578, implement @covariant parameter overrides

pkg/analyzer/lib/src/generated/resolver.dart

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index 4f99160925a80b62af7953f4b5852250e7efcd5d..ca8887c2d50896d4e589a71100f4019b2adf689a 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -533,8 +533,8 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
    * [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;
     }
@@ -7328,7 +7328,8 @@ class ResolverVisitor extends ScopedVisitor {
         !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;