fix #29544, mixins to a class with named constructors

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart

 // Copyright (c) 2015, 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.
 
 /// This library defines the operations that define and manipulate Dart
 /// classes.  Included in this are:
 ///   - Generics
 ///   - Class metadata
 ///   - Extension methods
 ///
@@ skipping 15 matching lines @@
     '''(() => {
   // Create an initializer for the mixin, so when derived constructor calls
   // super, we can correctly initialize base and mixins.
 
   // Create a class that will hold all of the mixin methods.
   class Mixin extends $base {}
   // Copy each mixin's methods, with later ones overwriting earlier entries.
   for (let m of $mixins) {
     $copyProperties(Mixin.prototype, m.prototype);
   }
-  // Initializer method: run mixin initializers, then the base.
+  // Initializer methods: run mixin initializers, then the base.
   Mixin.prototype.new = function(...args) {
     // Run mixin initializers. They cannot have arguments.
     // Run them backwards so most-derived mixin is initialized first.
     for (let i = $mixins.length - 1; i >= 0; i--) {
       $mixins[i].prototype.new.call(this);
     }
     // Run base initializer.
     $base.prototype.new.apply(this, args);
   };
+  if ($base[$_namedConstructors] != null) {

[Jennifer Messerly, 2017/05/03 19:43:55]

Just noticed while working on another CL: this should use `safeGetOwnProperty`
instead of [], because we only want to look at base.

Same thing below in defineNamedConstructor. I'll work on fixing those if it all
looks good to you, and add a test for the problematic case.

+    for (let namedCtor of $base[$_namedConstructors]) {
+      Mixin.prototype[namedCtor] = function(...args) {
+        // Run mixin initializers. They cannot have arguments.
+        // Run them backwards so most-derived mixin is initialized first.
+        for (let i = $mixins.length - 1; i >= 0; i--) {
+          $mixins[i].prototype.new.call(this);
+        }
+        // Run base initializer.
+        $base.prototype[namedCtor].apply(this, args);
+      };
+    }
+  }
 
   // Set the signature of the Mixin class to be the composition
   // of the signatures of the mixins.
   $setSignature(Mixin, {
     methods: () => {
       let s = {};
       for (let m of $mixins) {
         if (m[$_methodSig]) $copyProperties(s, m[$_methodSig]);
       }
       return s;
@@ skipping 361 matching lines @@
 /// function with the same name.
 ///
 /// After we define the named constructor, the class can be constructed with
 /// `new SomeClass.name(args)`.
 defineNamedConstructor(clazz, name) => JS(
     '',
     '''(() => {
   let proto = $clazz.prototype;
   let initMethod = proto[$name];
   let ctor = function(...args) { initMethod.apply(this, args); };
-  ctor[$isNamedConstructor] = true;
+  if ($clazz[$_namedConstructors] == null) $clazz[$_namedConstructors] = [];
+  $clazz[$_namedConstructors].push($name);
   ctor.prototype = proto;
   // Use defineProperty so we don't hit a property defined on Function,
   // like `caller` and `arguments`.
   $defineProperty($clazz, $name, { value: ctor, configurable: true });
 })()''');
 
+final _namedConstructors = JS('', 'Symbol("_namedConstructors")');
+
 final _extensionType = JS('', 'Symbol("extensionType")');
 
 getExtensionType(obj) => JS('', '#[#]', obj, _extensionType);
 
 final dartx = JS('', 'dartx');
 
 getExtensionSymbol(name) {
   var sym = JS('', 'dartx[#]', name);
   if (sym == null) {
     sym = JS('', 'Symbol("dartx." + #.toString())', name);
@@ skipping 207 matching lines @@
     '''(() => {
   let values = [];
   for (var i = 0; i < $names.length; i++) {
     let value = $const_(new $enumClass(i));
     values.push(value);
     Object.defineProperty($enumClass, $names[i],
         { value: value, configurable: true });
   }
   $enumClass.values = $constList(values, $enumClass);
 })()''');