Correct about the parens. I'm just going to fix it a the top level, without parens. There's no reason it shouldn't work, the fact that it doesn't work now is just an accident of implementation.

I'll fix it by adding a special test, the same way that != has a special test.

For those who say it shouldn't be allowed at the top level anyway, but should be allowed in parens: if we decide that (which I disagree with), then it should not be disallowed because of an accidental interaction with format specs. It should be explicitly checked for and disallowed. Again, I am not planning on making that change. I'm just going to allow it.