provide MISSING_RETURN on factory constructors

pkg/analyzer/test/generated/non_error_resolver_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.non_error_resolver_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
@@ skipping 2809 matching lines @@
   g = () => 0;
 }''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_invalidFactoryNameNotAClass() {
     Source source = addSource(r'''
 class A {
-  factory A() {}
+  factory A() => null;
 }''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_invalidIdentifierInAsync() {
     Source source = addSource(r'''
 class A {
   m() {
@@ skipping 643 matching lines @@
 }
 class B extends Object with A {}''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_mixinDeclaresConstructor_factory() {
     Source source = addSource(r'''
 class A {
-  factory A() {}
+  factory A() => null;
 }
 class B extends Object with A {}''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_mixinInheritsFromNotObject_classDeclaration_extends() {
     AnalysisOptionsImpl options = new AnalysisOptionsImpl();
     options.enableSuperMixins = true;
@@ skipping 763 matching lines @@
 }''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_nonGenerativeConstructor() {
     Source source = addSource(r'''
 class A {
   A.named() {}
-  factory A() {}
+  factory A() => null;
 }
 class B extends A {
   B() : super.named();
 }''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_nonTypeInCatchClause_isClass() {
@@ skipping 397 matching lines @@
 
   void test_recursiveFactoryRedirect() {
     Source source = addSource(r'''
 class A {
   factory A() = B;
 }
 class B implements A {
   factory B() = C;
 }
 class C implements B {
-  factory C() {}
+  factory C() => null;
 }''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_redirectToInvalidFunctionType() {
     Source source = addSource(r'''
 class A implements B {
   A(int p) {}
@@ skipping 1361 matching lines @@
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "a");
   }
 
   CompilationUnit _getResolvedLibraryUnit(Source source) =>
       analysisContext.getResolvedCompilationUnit2(source, source);
 }