These commands were trusting that elaboration resulted in type-correct
terms, but users testing custom elaborators have found it to be
surprising that they do not do typechecking. This adds a `Meta.check`
step.
Many of our tests in `tests/lean/run/` produce output from `#eval` (or
`#check`) statements, that is then ignored.
This PR tries to capture all the useful output using `#guard_msgs`. I've
only done a cursory check that the output is still sane --- there is a
chance that some "unchecked" tests have already accumulated regressions
and this just cements them!
In the other direction, I did identify two rotten tests:
* a minor one in `setStructInstNotation.lean`, where a comment says `Set
Nat`, but `#check` actually prints `?_`. Weird?
* `CompilerProbe.lean` is generating empty output, apparently indicating
that something is broken, but I don't know the signficance of this file.
In any case, I'll ask about these elsewhere.
(This started by noticing that a recent `grind` test file had an
untested `trace_state`, and then got carried away.)
@Kha It seems the recent parser modifications created some unexpected
problems. I didn't investigate them. I am "lost" in the elaborator and
dependent pattern matching land.
1) We can't write anymore
```
f [1, 2, 3] |>.run' 0 = Except.ok ()
```
We have to use parentheses and the error message is weird :(
```
(f [1, 2, 3] |>.run' 0) = Except.ok ()
```
2) I had to add comments to `macro.lean`, I didn't find a workaround
for one of the rules. BTW, I had to add a bunch of `:term` for fixing
the other rules, and the error messages were counterintuitive.
