Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
fa058ed228
Else the `case` will now allow introducing all necessary variables. Induction principles with `let` in the types of the cases will be more common with #3432. This implementation no longer reduces the type as it goes, but really only counts manifest foralls and lets. I find this more sensible and predictable: If you have ``` theorem induction₂_symm {P : EReal → EReal → Prop} (symm : Symmetric P) … ``` then previously, writing ``` case symm => ``` would actually bring a fresh `x` and `y` and variable `h : P x y` into scope and produce a goal of `P y x`, because `Symmetric P` happens to be ``` def Symmetric := ∀ ⦃x y⦄, x ≺ y → y ≺ x ``` After this change, after `case symm =>` will leave `Symmetric P` as the goal. This gives more control to the author of the induction hypothesis about the actual goal of the cases. This shows up in mathlib in two places; fixes in https://github.com/leanprover-community/mathlib4/pull/11023. I consider these improvements. |
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