When we expect a semicolon, we should be able to provide more standard
recovery.
Note this affects a test of `base`, but it looks like a partial
improvement (the prior line was moving too far). Still, it looks like
recovery isn't handling `{}` quite right. I'm not trying to address that
here though -- leaving a TODO.
This is something I noticed working on
https://github.com/carbon-language/carbon-lang/pull/3884; I think we
have more functions named Diagnose* at present than Emit* or Report*, so
just trying to consolidate. Note a couple Diagnose* functions do a
little more validation, but maybe those should actually be renamed away
(zygoloid had mentioned wanting to generally split out diagnostics to
their own function, and then we'd have it be a more common pattern).
Jon Ross-Perkins
Richard Smith