metalet with postfix improvement

lib/runtime/dart/_isolate_helper.js

Index: lib/runtime/dart/_isolate_helper.js
diff --git a/lib/runtime/dart/_isolate_helper.js b/lib/runtime/dart/_isolate_helper.js
index 3c53c4ccf53f9512936fd673fa5f663c9a157a7e..c1826816560e179bb9617012a2c1e5c50beefa44 100644
--- a/lib/runtime/dart/_isolate_helper.js
+++ b/lib/runtime/dart/_isolate_helper.js
@@ -358,13 +358,11 @@ var _isolate_helper;
   let _activeJsAsyncCount = Symbol('_activeJsAsyncCount');
   // Function enterJsAsync: () → dynamic
   function enterJsAsync() {
-    let o$ = exports._globalState.topEventLoop;
-    o$[_activeJsAsyncCount] = dart.notNull(o$[_activeJsAsyncCount]) + 1;
+    dart.prop(exports._globalState.topEventLoop, _activeJsAsyncCount).notNull++;

[vsm, 2015/04/09 16:58:28]

How about just specializing the increment case?  E.g.,

dart.dincrement(exports._globalState.topEventLoop, _activeJsAsyncCount)

with optional args for increment (1 by default) and perhaps pre/post (post by
default):

dart.dincrement(exports._globalState.topEventLoop, _activeJsAsyncCount, -1)

?

[Jennifer Messerly, 2015/04/09 17:47:40]

yeah, that could work, would we have different prefix vs postfix variants, or
only postifx?

Note the diff in this CL is a bit misleading, I only added support for postfix
so far, so prefix/op assign won't show up.

[vsm, 2015/04/10 00:14:10]

Another alternative:

dart.nullcheck(exports._globalState.topEventLoop, _activeJsAsyncCount)++;

i.e., fold the notNull and prop into one since it's such a common pattern.

In general, the fact that x.notNull++ changes x is surprising to me.

[Jennifer Messerly, 2015/04/10 01:00:24]

that won't work though ... it has to be an lvalue. The ".notNull" is so we get
an lvalue.

it could be: `dart.nullcheck(obj, prop).value` ... that was just more wordy,
only reason I didn't go for it.
yeah, it's all degrees of terrible, IMHO =\

   }
   // Function leaveJsAsync: () → dynamic
   function leaveJsAsync() {
-    let o$ = exports._globalState.topEventLoop;
-    o$[_activeJsAsyncCount] = dart.notNull(o$[_activeJsAsyncCount]) - 1;
+    dart.prop(exports._globalState.topEventLoop, _activeJsAsyncCount).notNull--;
     dart.assert(dart.notNull(exports._globalState.topEventLoop[_activeJsAsyncCount]) >= 0);
   }
   // Function isWorker: () → bool
@@ -483,11 +481,7 @@ var _isolate_helper;
   let _close = Symbol('_close');
   class _IsolateContext extends core.Object {
     _IsolateContext() {
-      this.id = (() => {
-        let o$ = exports._globalState, x$ = o$.nextIsolateId;
-        o$.nextIsolateId = dart.notNull(x$) + 1;
-        return x$;
-      })();
+      this.id = dart.prop(exports._globalState, 'nextIsolateId').notNull++;
       this.ports = new (core.Map$(core.int, RawReceivePortImpl))();
       this.weakPorts = new (core.Set$(core.int))();
       this.isolateStatics = _foreign_helper.JS_CREATE_ISOLATE();
@@ -1098,9 +1092,7 @@ var _isolate_helper;
         };
       }(_foreign_helper.DART_CLOSURE_TO_JS(IsolateNatives[_processWorkerMessage]), worker);
       worker.onmessage = processWorkerMessageTrampoline;
-      let o$ = exports._globalState;
-      let workerId = o$.nextManagerId;
-      o$.nextManagerId = dart.notNull(workerId) + 1;
+      let workerId = dart.prop(exports._globalState, 'nextManagerId').notNull++;
       IsolateNatives.workerIds.set(worker, workerId);
       exports._globalState.managers.set(workerId, worker);
       worker.postMessage(_serializeMessage(dart.map({command: 'start', id: workerId, replyTo: _serializeMessage(replyPort), args: args, msg: _serializeMessage(message), isSpawnUri: isSpawnUri, startPaused: startPaused, functionName: functionName})));