Preliminary Harmony weak maps API implementation.

test/mjsunit/harmony/weakmaps.js

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+
+// Flags: --harmony-weakmaps --expose-gc
+
+
+// Test valid getter and setter calls
+var m = new WeakMap;
+assertDoesNotThrow(function () { m.get(new Object) });
+assertDoesNotThrow(function () { m.set(new Object) });
+
+
+// Test invalid getter and setter calls
+var m = new WeakMap;
+assertThrows(function () { m.get(undefined) }, TypeError);
+assertThrows(function () { m.set(undefined, 0) }, TypeError);
+assertThrows(function () { m.get(0) }, TypeError);
+assertThrows(function () { m.set(0, 0) }, TypeError);
+assertThrows(function () { m.get('a-key') }, TypeError);
+assertThrows(function () { m.set('a-key', 0) }, TypeError);
+
+
+// Test expected mapping behavior
+var m = new WeakMap;
+function TestMapping(map, key, value) {
+  map.set(key, value);
+  assertSame(value, map.get(key));
+}
+TestMapping(m, new Object, 23);
+TestMapping(m, new Object, 'the-value');
+TestMapping(m, new Object, new Object);

[rossberg, 2011/08/02 12:33:38]

Does this work with proxies as keys?

[Michael Starzinger, 2011/08/02 14:05:22]

No, actually it doesn't. Unfortunately the whole concept of identity hash codes
is implemented on JSObject, but a JSProxy cannot be cast to a JSObject. So it
will require quite some effort to make it work.

Does the Harmony proposal for proxies say anything about identity hash codes for
proxies?

[rossberg, 2011/08/02 15:32:04]

In that case, some respective TODO in here would probably be good to have.
No, what specifically would you expect it to say? AFAICS, the spec never talks
about hashing or hash codes, nor should it.

[Michael Starzinger, 2011/08/02 16:04:51]

Done. Added comment to runtime.cc, that's were the assertion will trigger in
case you pass JSProxy objects.
Hmm, I am so used to identity hashing, can't imagine an OO-language without it.
:)

+
+
+// Test GC of map with entry
+var m = new WeakMap;
+var key = new Object;
+m.set(key, 'not-collected');
+gc();
+assertSame('not-collected', m.get(key));
+
+
+// Test GC of map with chained entries
+var m = new WeakMap;
+var head = new Object;
+for (key = head, i = 0; i < 10; i++, key = m.get(key)) {
+  m.set(key, new Object);
+}
+gc();
+var count = 0;
+for (key = head; key != undefined; key = m.get(key)) {
+  count++;
+}
+assertEquals(11, count);
+
+
+// Test property attribute [[Enumerable]]
+var m = new WeakMap;
+function props(x) {
+  var array = [];
+  for (var p in x) array.push(p);
+  return array.sort();
+}
+assertArrayEquals([], props(WeakMap));
+assertArrayEquals([], props(WeakMap.prototype));
+assertArrayEquals([], props(m));
+
+
+// Test some common JavaScript idioms
+var m = new WeakMap;
+assertTrue(m instanceof WeakMap);
+assertTrue(WeakMap.prototype.set instanceof Function)
+assertTrue(WeakMap.prototype.get instanceof Function)

[danno, 2011/08/02 12:48:02]

add test cases that set and get arbitrary properties and elements on a weak map,
especially ones designed to trigger fast in-object properties. 

[Michael Starzinger, 2011/08/02 14:05:22]

Done.