bug#16567: 24.3.50; pcase should signal an error if no case matches

[Stefan Monnier]

> Would `pcasex' be acceptable?

It's kind of ugly, and I'm not sure what the "x" stands for.

> I used xcase because I cannot come up with a good enough short name,
> and a long name for such a fundamental macro can be annoying.

`pcase-e TAB' should expand to `pcase-exhaustive', so the length is not
that troublesome, unless you're concerned about line-length and
indentation (in which case the length of `pcase-exhaustive' may indeed
occasionally force you to use an extra line).

I'm open to other suggestions, and `pcasex' is not unacceptable, so
I think we're closing in.


        Stefan