Better runtime type checks.

frog/lib/core.js

Index: frog/lib/core.js
diff --git a/frog/lib/core.js b/frog/lib/core.js
index 3f5a872d20b2612ba7b890d87dd0d8a912bc2f15..48b2b1370d1275ca75bcb08dc1183397920cade7 100644
--- a/frog/lib/core.js
+++ b/frog/lib/core.js
@@ -174,6 +174,13 @@ function $assert(test, text, url, line, column) {
   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.