always slice spread literals

lib/6to5/templates/call.js

@@ -0,0 +1 @@
+OBJECT.call(CONTEXT);

lib/6to5/transformers/spread.js

@@ -2,7 +2,18 @@ var util = require("../util");
 var b    = require("recast").types.builders;
 var _    = require("lodash");
 
-exports.ArrayExpression = function (node) {
+var getSpreadLiteral = function (spread, file) {
+  var literal = spread.argument;
+  if (literal.type !== "ArrayExpression") {
+    literal = util.template("call", {
+      OBJECT: file.addDeclaration("slice"),
+      CONTEXT: literal
+    });
+  }
+  return literal;
+};
+
+exports.ArrayExpression = function (node, parent, file) {
   var elements = node.elements;
   if (!elements.length) return;
 
@@ -13,7 +24,7 @@ exports.ArrayExpression = function (node) {
   }
 
   var concat = util.template("array-concat", {
-    ARGUMENT: spread.argument
+    ARGUMENT: getSpreadLiteral(spread, file)
   });
 
   concat.callee.object.elements = elements;
@@ -27,18 +38,12 @@ exports.CallExpression = function (node, parent, file) {
   if (args.length && _.last(args).type === "SpreadElement") {
     var spread = args.pop();
 
-    var spreadLiteral  = spread.argument;
+    var spreadLiteral  = getSpreadLiteral(spread, file);
     var contextLiteral = b.literal(null);
 
     node.arguments = [];
 
     if (args.length) {
-      if (spreadLiteral.name === "arguments") {
-        spreadLiteral = util.template("arguments-slice", {
-          SLICE_KEY: file.addDeclaration("slice")
-        });
-      }
-
       var concat = util.template("array-concat");
       concat.arguments = [spreadLiteral];
       concat.callee.object.elements = args;

test/fixtures/syntax/spread/array-literals/expected.js

@@ -1,5 +1,7 @@
+var _slice = Array.prototype.slice;
+
 var lyrics = [
   "head",
   "and",
   "toes"
-].concat(parts);
+].concat(_slice.call(parts));

test/fixtures/syntax/spread/contexted-method-call-multiple-args/expected.js

@@ -1,8 +1,9 @@
+var _slice = Array.prototype.slice;
 foob.add.apply(foob, [
   foo,
   bar
-].concat(numbers));
+].concat(_slice.call(numbers)));
 foob.test.add.apply(foob.test, [
   foo,
   bar
-].concat(numbers));
+].concat(_slice.call(numbers)));

test/fixtures/syntax/spread/contexted-method-call-single-arg/expected.js

@@ -1,2 +1,3 @@
-foob.add.apply(foob, numbers);
+var _slice = Array.prototype.slice;
-foob.test.add.apply(foob.test, numbers);
+foob.add.apply(foob, _slice.call(numbers));
+foob.test.add.apply(foob.test, _slice.call(numbers));

test/fixtures/syntax/spread/method-call-multiple-args/expected.js

@@ -1,4 +1,5 @@
+var _slice = Array.prototype.slice;
 add.apply(null, [
   foo,
   bar
-].concat(numbers));
+].concat(_slice.call(numbers)));

test/fixtures/syntax/spread/method-call-single-arg/expected.js

@@ -1 +1,2 @@
-add.apply(null, numbers);
+var _slice = Array.prototype.slice;
+add.apply(null, _slice.call(numbers));