This message is often incorporated into source files via `#guard_msgs`.
This change ensures it won't go over the 100 character ruler, and I
think is equally grammatical. :-)
It is confusing that the message suggesting to use the `diagnostics`
option is given even when the option is already set. This PR makes use
of lazy message data to make the message contingent on the option being
false.
It also tones down the promise that there is any diagonostic information
available, since sometimes there is nothing to report.
Suggested by Johan Commelin.
Summary:
- Take `synthPendingDepth` into account when caching TC results
- Add `maxSynthPendingDepth` option with default := 2.
- Add support for tracking `synthPending` failures when using
`set_option diagnostics true`
closes#2522closes#3313closes#3927
Identical to #4114 but with `maxSynthPendingDepth := 1`
closes#4114
cc @semorrison
This feature produced counterintuitive behavior and confused users.
See discussion at #770.
As pointed out by @tydeu, it is not too much work to write `Id.run <|`
before the `do` when we want to use the `do` notation in pure code.
closes#770
closes#318
Like Lean 3, we are doing it only for theorems.
@Kha, we talked about doing it for definitions too, it sounded like a
good idea, and it would make the system's behavior more uniform, but
unfortunately it creates too many problems. There are so many trivial
cases where it breaks. Here are some examples.
1- Definitions that take multiple bundled structures
```
def foo (s1 : Group) (s2 : CommRing) ...
```
They are universe polymorphic, and the different structures must be in
the same universe, but we don't know it when we elaborate the header,
that is, we need to elaborate the body.
An extreme case is `PUnit` occurring in the header. It is universe
polymorphic, but we only lear the constraints on this universe after
we elaborate the body.
2- All files containing unification hints broke.
Again, there are universe constraints on the header that we only learn
after we elaborate the body.
3- Many `CoeSort` and `CoeFun` examples broke.
Example:
```
structure Group :=
(carrier : Type u) (mul : carrier → carrier → carrier) (one : carrier)
instance GroupToType : CoeSort Group (Type u) :=
CoeSort.mk (fun g => g.carrier)
```
We would have to write
```
instance GroupToType : CoeSort Group.{u} (Type u) :=
CoeSort.mk (fun g => g.carrier)
```
We would have to provide universe level parameters manually in this
kind of instance. I think it would be too annoying.
