lean4-htt/tests/lean/run/array_simp.lean
Eric Wieser ae1ab94992
fix: replace bad simp lemmas for Id (#7352)
This PR reworks the `simp` set around the `Id` monad, to not elide or
unfold `pure` and `Id.run`

In particular, it stops encoding the "defeq abuse" of `Id X = X` in the
statements of theorems, instead using `Id.run` and `pure` to pass back
and forth between these two spellings. Often when writing these with
`pure`, they generalize to other lawful monads; though such changes were
split off to other PRs.

This fixes the problem with the current simp set where `Id.run (pure x)`
is simplified to `Id.run x`, instead of the desirable `x`.
This is particularly bad because the` x` is sometimes inferred with type
`Id X` instead of `X`, which prevents other `simp` lemmas about `X` from
firing.

Making `Id` reducible instead is not an option, as then the `Monad`
instances would have nothing to key on.

---------

Co-authored-by: Sebastian Graf <sg@lean-fro.org>
Co-authored-by: Kim Morrison <kim@tqft.net>
Co-authored-by: Paul Reichert <6992158+datokrat@users.noreply.github.com>
2025-05-22 22:45:35 +00:00

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attribute [-simp] Nat.default_eq_zero -- undo changes to simp set after this test was written
#check_simp #[1,2,3,4,5][2] ~> 3
#check_simp #[1,2,3,4,5][2]? ~> some 3
#check_simp #[1,2,3,4,5][7]? ~> none
#check_simp #[][0]? ~> none
#check_simp #[1,2,3,4,5][2]! ~> 3
#check_simp #[1,2,3,4,5][7]! ~> (default : Nat)
#check_simp (#[] : Array Nat)[0]! ~> (default : Nat)
variable {xs : Array α} in
#check_simp xs.size = 0 ~> xs = #[]
#check_simp
(Id.run do
let mut s := 0
for i in #[1,2,3,4] do
s := s + i
pure s) ~> 10
#check_simp
(Id.run do
let mut s := 0
for h : i in #[1,2,3,4] do
s := s + i
pure s) ~> 10