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lean4/tests/elab/1856.lean
Garmelon 08eb78a5b2 chore: switch to new test/bench suite (#12590)
This PR sets up the new integrated test/bench suite. It then migrates
all benchmarks and some related tests to the new suite. There's also
some documentation and some linting.

For now, a lot of the old tests are left alone so this PR doesn't become
even larger than it already is. Eventually, all tests should be migrated
to the new suite though so there isn't a confusing mix of two systems.
2026-02-25 13:51:53 +00:00

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structure Equiv (α : Sort _) (β : Sort _) where
toFun : α β
invFun : β α
left_inv : x, invFun (toFun x) = x
infixl:25 "" => Equiv
/-- A product of types can be split as the binary product of one of the types and the product
of all the remaining types. -/
def piSplitAt {α : Type _} [DecidableEq α] (i : α) (β : α Type _) :
( j, β j) β i × j : { j // j i }, β j where
toFun f := f i, fun j => f j
invFun f j := if h : j = i then h.symm.rec f.1 else f.2 j, h
left_inv f := by
apply funext
intro x
/- Goal is now:
```
(fun f j => if h : j = i then (_ : i = j) ▸ f.fst else Prod.snd f { val := j, property := h })
((fun f => (f i, fun j => f j.val)) f) x =
f x
```
-/
dsimp
trace_state
sorry