Issue 25650. Generate unique parameter names when create a method or function.

pkg/analysis_server/test/services/correction/fix_test.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 test.services.correction.fix;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/edit/fix/fix_core.dart';
 import 'package:analysis_server/plugin/edit/fix/fix_dart.dart';
@@ skipping 3764 matching lines @@
     await assertHasFix(
         DartFixKind.CHANGE_TO,
         '''
 class MyClass {}
 main() {
   MyClass v = null;
 }
 ''');
   }
 
+  test_undefinedFunction_create_duplicateArgumentNames() async {
+    resolveTestUnit('''
+class C {
+  int x;
+}
+
+foo(C c1, C c2) {
+  bar(c1.x, c2.x);
+}
+''');
+    await assertHasFix(
+        DartFixKind.CREATE_FUNCTION,
+        '''
+class C {
+  int x;
+}
+
+foo(C c1, C c2) {
+  bar(c1.x, c2.x);
+}
+
+void bar(int x, int x2) {
+}
+''');
+  }
+
   test_undefinedFunction_create_dynamicArgument() async {
     resolveTestUnit('''
 main() {
   dynamic v;
   test(v);
 }
 ''');
     await assertHasFix(
         DartFixKind.CREATE_FUNCTION,
         '''
@@ skipping 631 matching lines @@
 
   test_undefinedMethod_createQualified_targetIsUnresolved() async {
     resolveTestUnit('''
 main() {
   NoSuchClass.myUndefinedMethod();
 }
 ''');
     await assertNoFix(DartFixKind.CREATE_METHOD);
   }
 
+  test_undefinedMethod_createUnqualified_duplicateArgumentNames() async {
+    resolveTestUnit('''
+class C {
+  int x;
+}
+
+class D {
+  foo(C c1, C c2) {
+    bar(c1.x, c2.x);
+  }
+}''');
+    await assertHasFix(
+        DartFixKind.CREATE_METHOD,
+        '''
+class C {
+  int x;
+}
+
+class D {
+  foo(C c1, C c2) {
+    bar(c1.x, c2.x);
+  }
+
+  void bar(int x, int x2) {
+  }
+}''');
+  }
+
   test_undefinedMethod_createUnqualified_parameters() async {
     resolveTestUnit('''
 class A {
   main() {
     myUndefinedMethod(0, 1.0, '3');
   }
 }
 ''');
     await assertHasFix(
         DartFixKind.CREATE_METHOD,
@@ skipping 508 matching lines @@
       int offset = resultCode.indexOf(search);
       positions.add(new Position(testFile, offset));
     }
     return positions;
   }
 
   void _performAnalysis() {
     while (context.performAnalysisTask().hasMoreWork);
   }
 }