assertScriptCanLoadAsCJS() loads assertScriptCanLoadAsCJSImpl() on-demand.

It seems that with allowJs / checkJs enabled, our own loader hook is called during the loading process. This causes an error where assertScriptCanLoadAsCJSImpl is invoked before it's loaded.

Also, I need to be sure I understand why our tests weren't catching this before. Is it possible that the "ignore" rules have broken? Or is it that the test cases which uncovered this bug are explicitly disabling "ignore" patterns?