wrap instanceof to support @@hasInstance - fixes #1364

src/babel/transformation/file/index.js

@@ -85,6 +85,7 @@ export default class File {
     "temporal-assert-defined",
     "self-global",
     "default-props",
+    "instanceof",
 
     // legacy
     "interop-require",

src/babel/transformation/templates/helper-instanceof.js

@@ -0,0 +1,7 @@
+(function (left, right) {
+  if (right != null && right[Symbol.hasInstance]) {
+    return right[Symbol.hasInstance](left);
+  } else {
+    return left instanceof right;
+  }
+});

src/babel/transformation/transformers/es6/spec.symbols.js

@@ -5,14 +5,16 @@ export var metadata = {
 };
 
 export function UnaryExpression(node, parent, scope, file) {
-  this.skip();
+  if (node._ignoreSpecSymbols) return;
 
   if (node.operator === "typeof") {
     var call = t.callExpression(file.addHelper("typeof"), [node.argument]);
     if (this.get("argument").isIdentifier()) {
       var undefLiteral = t.literal("undefined");
+      var unary = t.unaryExpression("typeof", node.argument);
+      unary._ignoreSpecSymbols = true;
       return t.conditionalExpression(
-        t.binaryExpression("===", t.unaryExpression("typeof", node.argument), undefLiteral),
+        t.binaryExpression("===", unary, undefLiteral),
         undefLiteral,
         call
       );
@@ -22,6 +24,12 @@ export function UnaryExpression(node, parent, scope, file) {
   }
 }
 
+export function BinaryExpression(node, parent, scope, file) {
+  if (node.operator === "instanceof") {
+    return t.callExpression(file.addHelper("instanceof"), [node.left, node.right]);
+  }
+}
+
 export function VariableDeclaration(node) {
   if (node._generated) this.skip();
 }

test/core/fixtures/transformation/es6.spec.symbols/basic/expected.js

@@ -1,6 +0,0 @@
-"use strict";
-
-var _typeof = function (obj) { return obj && obj.constructor === Symbol ? "symbol" : typeof obj; };
-
-var s = Symbol("s");
-assert.equal(typeof s === "undefined" ? "undefined" : _typeof(s), "symbol");

test/core/fixtures/transformation/es6.spec.symbols/instanceof/actual.js

@@ -0,0 +1 @@
+a instanceof b;

test/core/fixtures/transformation/es6.spec.symbols/instanceof/exec.js

@@ -0,0 +1,21 @@
+var foo = { [Symbol.hasInstance]: function () { return true; } };
+var bar = {};
+
+assert.ok(bar instanceof foo);
+assert.ok(new String instanceof String);
+
+//
+
+function Greeting(greeting) {
+  this.greeting = greeting;
+}
+
+Greeting[Symbol.hasInstance] = function(inst) {
+  return inst.greeting == "hello";
+};
+
+var a = new Greeting("hello");
+var b = new Greeting("world");
+
+assert.ok(a instanceof Greeting);
+assert.ok(!(b instanceof Greeting));

test/core/fixtures/transformation/es6.spec.symbols/instanceof/expected.js

@@ -0,0 +1,3 @@
+"use strict";
+
+babelHelpers._instanceof(a, b);

test/core/fixtures/transformation/es6.spec.symbols/options.json

@@ -1,3 +1,4 @@
 {
+  "externalHelpers": true,
   "optional": ["es6.spec.symbols"]
 }

test/core/fixtures/transformation/es6.spec.symbols/typeof/actual.js

@@ -1,2 +1,3 @@
 var s = Symbol("s");
 assert.equal(typeof s, "symbol");
+assert.equal(typeof typeof s.foo, "symbol");

test/core/fixtures/transformation/es6.spec.symbols/typeof/expected.js

@@ -0,0 +1,5 @@
+"use strict";
+
+var s = Symbol("s");
+assert.equal(typeof s === "undefined" ? "undefined" : babelHelpers._typeof(s), "symbol");
+assert.equal(babelHelpers._typeof(babelHelpers._typeof(s.foo)), "symbol");