use Array.from instead of Array.prototype.slice in spread transformer and support NewExpression spreads - fixes #148

lib/6to5/templates/values.js

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

lib/6to5/transformation/transformers/spread.js

@@ -5,10 +5,10 @@ var _    = require("lodash");
 var getSpreadLiteral = function (spread, file) {
   var literal = spread.argument;
   if (!t.isArrayExpression(literal)) {
-    literal = util.template("call", {
-      OBJECT: file.addDeclaration("slice"),
-      CONTEXT: literal
-    });
+    literal = t.callExpression(
+      t.memberExpression(t.identifier("Array"), t.identifier("from")),
+      [literal]
+    );
   }
   return literal;
 };
@@ -96,3 +96,19 @@ exports.CallExpression = function (node, parent, file) {
 
   node.arguments.unshift(contextLiteral);
 };
+
+exports.NewExpression = function (node, parent, file) {
+  var args = node.arguments;
+  if (!hasSpread(args)) return;
+
+  var nodes = build(args, file);
+  var first = nodes.shift();
+
+  if (nodes.length) {
+    args = t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes);
+  } else {
+    args = first;
+  }
+
+  return t.callExpression(file.addDeclaration("apply-constructor"), [node.callee, args]);
+};

lib/6to5/types/builder-keys.json

@@ -12,6 +12,7 @@
   "IfStatement":             ["test", "consequent", "alternate"],
   "Literal":                 ["value"],
   "MemberExpression":        ["object", "property", "computed"],
+  "NewExpression":           ["callee", "arguments"],
   "ObjectExpression":        ["properties"],
   "ParenthesizedExpression": ["expression"],
   "Program":                 ["body"],