This PR improves the error messages produced by invalid projections and
field notation. It also adds a hint to the "function expected" error
message noting the argument to which the term is being applied, which
can be helpful for debugging spurious "function expected" messages
actually caused by syntax errors.
---------
Co-authored-by: Joachim Breitner <mail@joachim-breitner.de>
This PR makes `#guard_msgs` to treat `trace` messages separate from
`info`, `warning` and `error`. It also introduce the ability to say
`#guard_msgs (pass info`, like `(drop info)` so far, and also adds
`(check info)` as the explicit form of `(info)`, for completeness.
Fixes#8266
This PR makes the `change` tactic and conv tactic use the same
elaboration strategy. It works uniformly for both the target and local
hypotheses. Now `change` can assign metavariables, for example:
```lean
example (x y z : Nat) : x + y = z := by
change ?a = _
let w := ?a
-- now `w : Nat := x + y`
```
