Propertly tree shake factory constructors.

pkg/analyzer2dart/test/tree_shaker_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.
 
 import 'mock_sdk.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 161 matching lines @@
 }
 main() {
   new A().f1;
 }
 ''');
     helper.assertHasField('A.f1');
     helper.assertNoField('A.f2');
     helper.assertNoField('B.f1');
     helper.assertNoField('B.f2');
   });
+
+  test('Ordinary constructor with initializer list', () {
+    var helper = new TreeShakerTestHelper('''
+class A {
+  A() : x = f();
+  var x;
+  foo() {}
+}
+f() {}
+main() {
+  new A().foo();
+}
+''');
+    helper.assertHasMethod('A.foo');
+    helper.assertHasFunction('f');
+  });
+
+  test('Redirecting constructor', () {
+    var helper = new TreeShakerTestHelper('''
+class A {
+  A.a1() : this.a2();
+  A.a2();
+  foo() {}
+}
+main() {
+  new A.a1().foo();
+}
+''');
+    helper.assertHasMethod('A.foo');
+  });
+
+  test('Factory constructor', () {
+    var helper = new TreeShakerTestHelper('''
+class A {
+  factory A() {
+    return new B();
+  }
+  foo() {}
+}
+class B {
+  B();
+  foo() {}
+}
+main() {
+  new A().foo();
+}
+''');
+    helper.assertHasMethod('B.foo');
+    helper.assertNoMethod('A.foo');
+  });
+
+  test('Redirecting factory constructor', () {
+    var helper = new TreeShakerTestHelper('''
+class A {
+  factory A() = B;
+  foo() {}
+}
+class B {
+  B();
+  foo() {}
+}
+main() {
+  new A().foo();
+}
+''');
+    helper.assertHasMethod('B.foo');
+    helper.assertNoMethod('A.foo');
+  });
 }
 
 class TreeShakerTestHelper {
   /**
    * The name of the root file.
    */
   String rootFile = '/root.dart';
 
   /**
    * ClosedWorld that resulted from tree shaking.
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   /**
    * Asserts that [world] doesn't contain a method with the given qualified
    * name.
    *
    * [qualifiedName] - the qualified name in form 'className.methodName'.
    */
   void assertNoMethod(String qualifiedName) {
     expect(methods, isNot(contains(qualifiedName)));
   }
 }