provide MISSING_RETURN on factory constructors

pkg/analyzer/test/generated/compile_time_error_code_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 analyzer.test.generated.compile_time_error_code_test;
 
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:analyzer/src/generated/source_io.dart';
@@ skipping 2191 matching lines @@
     computeLibrarySourceErrors(source);
     assertErrors(source,
         [CompileTimeErrorCode.FIELD_INITIALIZED_IN_PARAMETER_AND_INITIALIZER]);
     verify([source]);
   }
 
   void test_fieldInitializerFactoryConstructor() {
     Source source = addSource(r'''
 class A {
   int x;
-  factory A(this.x) {}
+  factory A(this.x) => null;
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(
         source, [CompileTimeErrorCode.FIELD_INITIALIZER_FACTORY_CONSTRUCTOR]);
     verify([source]);
   }
 
   void test_fieldInitializerOutsideConstructor() {
     // TODO(brianwilkerson) Fix the duplicate error messages.
     Source source = addSource(r'''
@@ skipping 971 matching lines @@
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.INVALID_CONSTRUCTOR_NAME]);
     // no verify() call, "B" is not resolved
   }
 
   void test_invalidFactoryNameNotAClass_notClassName() {
     Source source = addSource(r'''
 int B;
 class A {
-  factory B() {}
+  factory B() => null;
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(
         source, [CompileTimeErrorCode.INVALID_FACTORY_NAME_NOT_A_CLASS]);
     verify([source]);
   }
 
   void test_invalidFactoryNameNotAClass_notEnclosingClassName() {
     Source source = addSource(r'''
 class A {
-  factory B() {}
+  factory B() => null;
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(
         source, [CompileTimeErrorCode.INVALID_FACTORY_NAME_NOT_A_CLASS]);
     // no verify() call, "B" is not resolved
   }
 
   void test_invalidModifierOnConstructor_async() {
     Source source = addSource(r'''
 class A {
@@ skipping 1503 matching lines @@
 }'''
     ], <ErrorCode>[
       CompileTimeErrorCode
           .NON_CONSTANT_VALUE_IN_INITIALIZER_FROM_DEFERRED_LIBRARY
     ]);
   }
 
   void test_nonGenerativeConstructor_explicit() {
     Source source = addSource(r'''
 class A {
-  factory A.named() {}
+  factory A.named() => null;
 }
 class B extends A {
   B() : super.named();
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.NON_GENERATIVE_CONSTRUCTOR]);
     verify([source]);
   }
 
   void test_nonGenerativeConstructor_implicit() {
     Source source = addSource(r'''
 class A {
-  factory A() {}
+  factory A() => null;
 }
 class B extends A {
   B();
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.NON_GENERATIVE_CONSTRUCTOR]);
     verify([source]);
   }
 
   void test_nonGenerativeConstructor_implicit2() {
     Source source = addSource(r'''
 class A {
-  factory A() {}
+  factory A() => null;
 }
 class B extends A {
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.NON_GENERATIVE_CONSTRUCTOR]);
     verify([source]);
   }
 
   void test_notEnoughRequiredArguments_const() {
     Source source = addSource(r'''
@@ skipping 977 matching lines @@
   }
 
   void test_superInInvalidContext_factoryConstructor() {
     Source source = addSource(r'''
 class A {
   m() {}
 }
 class B extends A {
   factory B() {
     super.m();
+    return null;
   }
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [CompileTimeErrorCode.SUPER_IN_INVALID_CONTEXT]);
     // no verify(), 'super.m' is not resolved
   }
 
   void test_superInInvalidContext_instanceVariableInitializer() {
     Source source = addSource(r'''
 class A {
@@ skipping 564 matching lines @@
         source, [CompileTimeErrorCode.WRONG_NUMBER_OF_PARAMETERS_FOR_OPERATOR]);
     verify([source]);
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "");
     _check_wrongNumberOfParametersForOperator(name, "a, b");
   }
 }