Issue 25623. When adding the 'async' modifier, change the return type.

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 334 matching lines @@
 
 part of my.lib;
 
 class A {}
 ''');
   }
 
   test_addSync_asyncFor() async {
     resolveTestUnit('''
 import 'dart:async';
-main(Stream<String> names) {
+void main(Stream<String> names) {
   await for (String name in names) {
     print(name);
   }
 }
 ''');
     await assertHasFix(
         DartFixKind.ADD_ASYNC,
         '''
 import 'dart:async';
-main(Stream<String> names) async {
+Future main(Stream<String> names) async {
   await for (String name in names) {
     print(name);
   }
 }
 ''');
   }
 
   test_addSync_BAD_nullFunctionBody() async {
     resolveTestUnit('''
 var F = await;
@@ skipping 50 matching lines @@
 main() => await foo();
 ''');
     await assertHasFix(
         DartFixKind.ADD_ASYNC,
         '''
 foo() {}
 main() async => await foo();
 ''');
   }
 
+  test_addSync_returnFuture() async {
+    errorFilter = (AnalysisError error) {
+      return error.errorCode == StaticWarningCode.UNDEFINED_IDENTIFIER;
+    };
+    resolveTestUnit('''
+foo() {}
+int main() {
+  await foo();
+  return 42;
+}
+''');
+    await assertHasFix(
+        DartFixKind.ADD_ASYNC,
+        '''
+import 'dart:async';
+
+foo() {}
+Future<int> main() async {
+  await foo();
+  return 42;
+}
+''');
+  }
+
+  test_addSync_returnFuture_alreadyFuture() async {
+    errorFilter = (AnalysisError error) {
+      return error.errorCode == StaticWarningCode.UNDEFINED_IDENTIFIER;
+    };
+    resolveTestUnit('''
+import 'dart:async';
+foo() {}
+Future<int> main() {
+  await foo();
+  return 42;
+}
+''');
+    await assertHasFix(
+        DartFixKind.ADD_ASYNC,
+        '''
+import 'dart:async';
+foo() {}
+Future<int> main() async {
+  await foo();
+  return 42;
+}
+''');
+  }
+
+  test_addSync_returnFuture_dynamic() async {
+    errorFilter = (AnalysisError error) {
+      return error.errorCode == StaticWarningCode.UNDEFINED_IDENTIFIER;
+    };
+    resolveTestUnit('''
+foo() {}
+dynamic main() {
+  await foo();
+  return 42;
+}
+''');
+    await assertHasFix(
+        DartFixKind.ADD_ASYNC,
+        '''
+foo() {}
+dynamic main() async {
+  await foo();
+  return 42;
+}
+''');
+  }
+
+  test_addSync_returnFuture_noType() async {
+    errorFilter = (AnalysisError error) {
+      return error.errorCode == StaticWarningCode.UNDEFINED_IDENTIFIER;
+    };
+    resolveTestUnit('''
+foo() {}
+main() {
+  await foo();
+  return 42;
+}
+''');
+    await assertHasFix(
+        DartFixKind.ADD_ASYNC,
+        '''
+foo() {}
+main() async {
+  await foo();
+  return 42;
+}
+''');
+  }
+
   test_boolean() async {
     resolveTestUnit('''
 main() {
   boolean v;
 }
 ''');
     await assertHasFix(
         DartFixKind.REPLACE_BOOLEAN_WITH_BOOL,
         '''
 main() {
@@ skipping 4389 matching lines @@
       int offset = resultCode.indexOf(search);
       positions.add(new Position(testFile, offset));
     }
     return positions;
   }
 
   void _performAnalysis() {
     while (context.performAnalysisTask().hasMoreWork);
   }
 }