I'm more used to !!x but that's just me.

Oh right, I forgot about that way of doing it. Just a sec.

Warning is gone on the buildbot, lgtm.

@lioncash What about the other 88 or so instances of this particular warning?

Does this warning really provide any value? I'd be in favor of just disabling it.

As I understand it, this warning only exists to make people aware that an assignment like this has a runtime cost and might be avoidable by propagating the bool type. That's pretty obvious and I'm in favor of disabling it.

The warning is because typically the conversion to bool is used when you want to test for true or false. But, the compiler must first cast the source type to bool and then test that result. Essentially that amounts to testing the value twice. This may or may not actually result in runtime overhead (actually, it's pretty unlikely).
However, the warning is good for detecting when you are implicitly converting a function argument to bool. This can alert you about the wrong function/template being selected, or that the code should just be reworked to use the correct types.

Anyways, lgtm.