add apply-constructor declaration and add support for not returning generated code in opts.code

lib/6to5/file.js

@@ -18,7 +18,7 @@ function File(opts) {
   this.ast          = {};
 }
 
-File.declarations = ["extends", "class-props", "slice"];
+File.declarations = ["extends", "class-props", "slice", "apply-constructor"];
 
 File.normaliseOptions = function (opts) {
   opts = _.cloneDeep(opts || {});
@@ -30,7 +30,8 @@ File.normaliseOptions = function (opts) {
     sourceMap:  false,
     filename:   "unknown",
     modules:    "common",
-    runtime:    false
+    runtime:    false,
+    code:       true
   });
 
   // normalise windows path separators to unix
@@ -142,6 +143,14 @@ File.prototype.generate = function () {
   var opts = this.opts;
   var ast  = this.ast;
 
+  if (!opts.code) {
+    return {
+      code: "",
+      map:  null,
+      ast:  ast
+    };
+  }
+
   var result = generate(ast, opts, this.code);
 
   if (this.shebang) {
@@ -153,6 +162,8 @@ File.prototype.generate = function () {
     result.code += "\n" + util.sourceMapToComment(result.map);
   }
 
+  result.ast = result;
+
   return result;
 };
 

lib/6to5/templates/apply-constructor.js

@@ -0,0 +1,5 @@
+(function (Constructor, args) {
+  var bindArgs = [null].concat(args);
+  var Factory = Constructor.bind.apply(Constructor, bindArgs);
+  return new Factory;
+});

lib/6to5/templates/values.js

@@ -0,0 +1,5 @@
+(function (obj) {
+  var arr = [];
+  for (var val of obj) arr.push(val);
+  return arr;
+});