We are considering removing `.` as an alternative for `·` in the
lambda dot notation (e.g., `(·+·)`).
Reasons:
- `.` is not a perfect replacement for `·` (e.g., `(·.insert ·)`)
- `.` is too overloaded: `(f.x)` and `(f .x)` and `(f . x)`. We want to keep the first two.
We don't use the following hack anymore:
- /- HACK: `fvarId` is not in the scope of `mvarId`
- If this generates problems in the future, we should update the metavariable declarations. -/
- assignExprMVar mvarId (mkFVar fvarId)
This hack was corrupting the `InfoTree`.
for regression introduced by the following change
* Auto implicit behavior changed for inductive families. An auto implicit argument occurring in inductive family index is also treated as an index (IF it is not fixed, see next item)
This modification is relevant for fixing regressions on recent changes
to the auto implicit behavior for inductive families.
The following declarations are now accepted:
```lean
inductive HasType : Fin n → Vector Ty n → Ty → Type where
| stop : HasType 0 (ty :: ctx) ty
| pop : HasType k ctx ty → HasType k.succ (u :: ctx) ty
inductive Sublist : List α → List α → Prop
| slnil : Sublist [] []
| cons l₁ l₂ a : Sublist l₁ l₂ → Sublist l₁ (a :: l₂)
| cons2 l₁ l₂ a : Sublist l₁ l₂ → Sublist (a :: l₁) (a :: l₂)
inductive Lst : Type u → Type u
| nil : Lst α
| cons : α → Lst α → Lst α
```
TODO: universe inference for `inductive` should be improved. The
current approach is not good enough when we have auto implicits.
TODO: allow implicit fixed indices that do not depend on indices that
cannot be moved to become parameters.
TODO: convert fixed indices to parameters. Motivation: types such as
```lean
inductive Foo : List α → Type
| mk : Foo []
```
Users should not need to write
```lean
inductive Foo {α} : List α → Type
| mk : Foo []
```
- Wait for all terms to be elaborated before showing folding regions.
May want to change this to support partial results.
- Use .span to extract import statements, rather than mutually
recursive functions.
- Some tiny other bits of cleanup
