lean4-htt/tests/lean/run/univIssue.lean at cd4cd581bea8a5e89d41a708564202f974cecd00 - max/lean4-htt - maxgit: wireguard access, git repository.

max/lean4-htt

Leonardo de Moura 79609938a8 feat: allow universe constraints to be postponed longer

Before this commit, each `isDefEq u v` invocation would fail if there
were pending universe level constraints. This commit, moves the
postponed universe constraints back to the `MetaM` state.
It also adds the combinator
```lean
withoutPostponingUniverseConstraints x
```
which executes `x` and throws an error if there are pending universe
constraints. We use the combinator at `elabApp` and `elabBinders`.
Without this commit, we would fail to elaborate simple terms such as
```lean
  Functor.map Prod.fst (x s)
```
because after elaborating `Prod.fst` and trying to ensure its type
match the expected one, we would be stuck at the universe constraint:
```
  u =?= max u ?v
```

Another benefit of the new approach is better error messages. Instead
of getting a mysterious type mismatch constraint, we get a list of
universe contraints the system is stuck at.

cc @Kha

2020-10-26 15:50:05 -07:00

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 universes u v
 @[inline] def ex1 {σ : Type u} {m : Type u → Type v} [Functor m] {α : Type u} (x : StateT σ m α) (s : σ) : m α :=
   Functor.map Prod.fst (x s)
 @[inline] def ex2 {σ : Type u} {m : Type u → Type v} [Functor m] {α : Type u} (x : StateT σ m α) (s : σ) : m α :=
   Prod.fst <$> x s