dart2js: Pass type information to constructor rather than add later.

pkg/compiler/lib/src/js_emitter/class_stub_generator.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.
 
 part of dart2js.js_emitter;
 
 class ClassStubGenerator {
   final Namer namer;
   final Compiler compiler;
   final JavaScriptBackend backend;
 
   ClassStubGenerator(this.compiler, this.namer, this.backend);
 
   jsAst.Expression generateClassConstructor(
-      ClassElement classElement, Iterable<jsAst.Name> fields) {
+      ClassElement classElement, Iterable<jsAst.Name> fields, bool hasRti) {
     // TODO(sra): Implement placeholders in VariableDeclaration position:
     //
     //     String constructorName = namer.getNameOfClass(classElement);
     //     return js.statement('function #(#) { #; }',
     //        [ constructorName, fields,
     //            fields.map(
     //                (name) => js('this.# = #', [name, name]))]));
-    return js('function(#) { #; this.#();}', [
+    var typeParameters = const <jsAst.Parameter>[];
+    var typeInits = const <jsAst.Expression>[];
+    if (hasRti) {
+      String parameterName = r'$ti';
+      typeParameters = parameterName;
+      typeInits = js('this.# = #', [namer.rtiFieldName, parameterName]);
+    }
+    return js('function(#, #) { #; #; this.#();}', [
       fields,
+      typeParameters,

[Siggi Cherem (dart-lang), 2016/08/19 16:39:46]

does js_ast remove the extra argument if typeParameters is an empty list? Or do
we need 2 templates function(#) {} and function(#, #) {} ?

[sra1, 2017/02/23 23:46:41]

# in most repeated contexts will spread a template argument that is an Iterable.
 So "function(#, #) ..." will append two parameter lists.

       fields.map((name) => js('this.# = #', [name, name])),
+      typeInits,
       namer.deferredAction
     ]);
   }
 
   jsAst.Expression generateGetter(Element member, jsAst.Name fieldName) {
     ClassElement cls = member.enclosingClass;
     String receiver = backend.isInterceptorClass(cls) ? 'receiver' : 'this';
     List<String> args = backend.isInterceptedMethod(member) ? ['receiver'] : [];
     return js('function(#) { return #.# }', [args, receiver, fieldName]);
   }
@@ skipping 245 matching lines @@
               if (cache === void 0) cache = #tearOff(
                   this, funcs, reflectionInfo, true, [], name).prototype;
               return cache;
             }
           : tearOffGetter(funcs, reflectionInfo, name, isIntercepted);
     }''',
       {'tearOff': tearOffAccessExpression});
 
   return <jsAst.Statement>[tearOffGetter, tearOff];
 }