fix #25305, DeclarationResolver.visitTypeParameter now handles generic methods

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/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 2359 matching lines @@
     for (Label label in node.labels) {
       SimpleIdentifier labelName = label.label;
       _findIdentifier(_enclosingExecutable.labels, labelName);
     }
     return super.visitSwitchDefault(node);
   }
 
   @override
   Object visitTypeParameter(TypeParameter node) {
     SimpleIdentifier parameterName = node.name;
-    if (_enclosingClass != null) {
-      _findIdentifier(_enclosingClass.typeParameters, parameterName);
-    } else if (_enclosingAlias != null) {
-      _findIdentifier(_enclosingAlias.typeParameters, parameterName);
+
+    Element element;
+    if (_enclosingExecutable != null) {
+      element =
+          _findIdentifier(_enclosingExecutable.typeParameters, parameterName);
+    }
+    if (element == null) {
+      if (_enclosingClass != null) {
+        _findIdentifier(_enclosingClass.typeParameters, parameterName);
+      } else if (_enclosingAlias != null) {
+        _findIdentifier(_enclosingAlias.typeParameters, parameterName);
+      }
     }
     return super.visitTypeParameter(node);
   }
 
   @override
   Object visitVariableDeclaration(VariableDeclaration node) {
     VariableElement element = null;
     SimpleIdentifier variableName = node.name;
     if (_enclosingExecutable != null) {
       element =
@@ skipping 10953 matching lines @@
     nonFields.add(node);
     return null;
   }
 
   @override
   Object visitNode(AstNode node) => node.accept(TypeResolverVisitor_this);
 
   @override
   Object visitWithClause(WithClause node) => null;
 }