[proxies] Correctly handle proxies in Function.prototype.bind

test/mjsunit/function-bind.js

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-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --harmony-proxies --harmony-reflect
 
-// Tests the Function.prototype.bind (ES 15.3.4.5) method.
+// Tests the Function.prototype.bind method.
+
 
 // Simple tests.
 function foo(x, y, z) {
   return [this, arguments.length, x];
 }
 
 assertEquals(3, foo.length);
 
 var f = foo.bind(foo);
 assertEquals([foo, 3, 1], f(1, 2, 3));
@@ skipping 269 matching lines @@
   var bound = fun.bind({});
   assertEquals(proto, Object.getPrototypeOf(bound));
 
   var bound2 = fun.bind({});
   assertTrue(%HaveSameMap(new bound, new bound2));
 
   Object.setPrototypeOf(fun, null);
   bound = Function.prototype.bind.call(fun, {});
   assertEquals(null, Object.getPrototypeOf(bound));
 })();
+
+
+
+///////////////////////////////////////////////////////////////////////////////
+// Proxies
+
+
+var log = [];
+var logger = {};
+var handler = new Proxy({}, logger);
+
+logger.get = function(t, trap, r) {
+  return function() {
+    log.push([trap, ...arguments]);
+    return Reflect[trap](...arguments);
+  }
+};
+
+
+// Simple case
+
+var target = function(a, b, c) { "use strict"; return this };
+var proxy = new Proxy(target, handler);
+var this_value = Symbol();
+
+log.length = 0;
+result = Function.prototype.bind.call(proxy, this_value, "foo");
+assertEquals(2, result.length);
+assertEquals(this_value, result());
+assertEquals(4, log.length);
+for (var i in log) assertSame(target, log[i][1]);
+assertEquals(["getOwnPropertyDescriptor", target, "length"], log[0]);
+assertEquals(["get", target, "length", proxy], log[1]);
+assertEquals(["get", target, "name", proxy], log[2]);
+assertEquals(["apply", target, this_value, ["foo"]], log[3]);

[Camillo Bruni, 2015/12/16 13:19:06]

Could you add another test where you check the log for GetPrototypeOf call in
9.4.1.3 BoundFunctionCreate (just make sure we totally respect the order of all
these calls)?

And you might need another test with a Constructable proxy (again 9.4.1.3)?

[neis, 2015/12/16 14:00:24]

As discussed, the getPrototypeOf should already have shown up here, so the
implementation of BoundFunctionCreate is indeed wrong as well.  Will update the
CL.

+
+
+// Custom length
+
+handler = {
+  get() {return 42},
+  getOwnPropertyDescriptor() {return {configurable: true}}
+};
+proxy = new Proxy(target, handler);
+
+result = Function.prototype.bind.call(proxy, this_value, "foo");
+assertEquals(41, result.length);
+assertEquals(this_value, result());
+
+
+// Long length
+
+handler = {
+  get() {return Math.pow(2, 100)},
+  getOwnPropertyDescriptor() {return {configurable: true}}
+};
+proxy = new Proxy(target, handler);
+
+result = Function.prototype.bind.call(proxy, this_value, "foo");
+assertEquals(Math.pow(2, 100) - 1, result.length);
+assertEquals(this_value, result());
+
+
+// Very long length
+
+handler = {
+  get() {return 1/0},
+  getOwnPropertyDescriptor() {return {configurable: true}}
+};
+proxy = new Proxy(target, handler);
+
+result = Function.prototype.bind.call(proxy, this_value, "foo");
+assertEquals(1/0, result.length);
+assertEquals(this_value, result());
+
+
+// Non-integer length
+
+handler = {
+  get() {return 4.2},
+  getOwnPropertyDescriptor() {return {configurable: true}}
+};
+proxy = new Proxy(target, handler);
+
+result = Function.prototype.bind.call(proxy, this_value, "foo");
+assertEquals(3, result.length);
+assertEquals(this_value, result());
+
+
+// Undefined length
+
+handler = {
+  get() {},
+  getOwnPropertyDescriptor() {return {configurable: true}}
+};
+proxy = new Proxy(target, handler);
+
+result = Function.prototype.bind.call(proxy, this_value, "foo");
+assertEquals(0, result.length);
+assertEquals(this_value, result());
+
+
+// Non-callable
+
+assertThrows(() => Function.prototype.bind.call(new Proxy({}, {})), TypeError);
+assertThrows(() => Function.prototype.bind.call(new Proxy([], {})), TypeError);