Better runtime type checks.

frog/lib/core.js

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // TODO(jimhug): Completeness - see tests/corelib
 
 /** Implements extends for dart classes on javascript prototypes. */
 function $inherits(child, parent) {
   if (child.prototype.__proto__) {
     child.prototype.__proto__ = parent.prototype;
@@ skipping 156 matching lines @@
     ret.$setindex(items[i++], items[i++]);
   }
   return ret;
 }
 
 function $assert(test, text, url, line, column) {
   if (typeof test == 'function') test = test();
   if (!test) $throw(new AssertError(text, url, line, column));
 }
 
+function $notnull_bool(test) {
+  if (test == null || typeof(test) != 'boolean') {
+    $throw(new TypeError('must be "true" or "false"'));
+  }
+  return test === true;

[jimhug, 2011/11/07 16:41:26]

I wonder if this would be better?

(possibly inlined at call sites?)

return test === true ? true : test === false ? false : $bool_error();

It seems like this could also be further optimized for if/else branches by using
the if (test === true) ... else { assert(test === false); ...} pattern.

[Jennifer Messerly, 2011/11/08 03:56:16]

I was mostly trying to keep checked mode relatively readable, hence going
through the method. I agree it'd be good to try a few different patterns and see
if we can get it inlined.

However I suspect once we start tracking non-nullable bools (e.g. anything that
is a result of a non-overloaded == or != operator or && || ! operator) we will
be able to eliminate a lot of the checks.

+}
+
 function $throw(e) {
   // If e is not a value, we can use V8's captureStackTrace utility method.
   // TODO(jmesserly): capture the stack trace on other JS engines.
   if (e && (typeof e == "object") && Error.captureStackTrace) {
     // TODO(jmesserly): this will clobber the e.stack property
     Error.captureStackTrace(e, $throw);
   }
   throw e;
 }
 
@@ skipping 135 matching lines @@
   // Get the prototype to patch.
   // Don't overwrite an existing stub, like the one on Object.prototype
   var proto = Object.getPrototypeOf(obj);
   if (!proto || proto.hasOwnProperty(name)) proto = obj;
   var method;
   while (obj && !(method = methods[obj.get$typeName()])) {
     obj = Object.getPrototypeOf(obj);
   }
   Object.defineProperty(proto, name, {value: method || methods['Object']});
 }