2 commits

Author	SHA1	Message	Date
Kyle Miller	249530f3c1	feat: partial inhabitation uses local Inhabited instances created from parameters (#5821) ... Rather than having a special pass where `mkInhabitantFor` uses the `assumption` tactic, it creates `Inhabited` instances for each parameter and just searches for an `Inhabited`/`Nonempty` instance for the return type. This makes examples like the following work: ```lean partial def f (x : X) : Bool × X := ... ``` Removes the strategy where it looks for `Inhabited`/`Nonempty` instances for every suffix of the signature. This is a follow-up to #5780. Motivated [by Zulip](https://leanprover.zulipchat.com/#narrow/channel/113489-new-members/topic/Why.20return.20type.20of.20partial.20function.20MUST.20.60inhabited.60.3F/near/477905312).	2024-10-23 18:15:31 +00:00
Kyle Miller	66dbad911e	fix: improve error message for partial inhabitation and add delta deriving (#5780) ... Example new output: ```text failed to compile 'partial' definition 'checkMyList', could not prove that the type ListNode → Bool × ListNode is nonempty. This process uses multiple strategies: - It looks for a parameter that matches the return type. - It tries synthesizing 'Inhabited' and 'Nonempty' instances for the return type. - It tries unfolding the return type. If the return type is defined using the 'structure' or 'inductive' command, you can try adding a 'deriving Nonempty' clause to it. ``` The inhabitation prover now also unfolds definitions when trying to prove inhabitation. For example, ```lean def T (α : Type) := α × α partial def f (n : Nat) : T Nat := f n ``` Motivated [by Zulip](https://leanprover.zulipchat.com/#narrow/channel/113489-new-members/topic/Why.20return.20type.20of.20partial.20function.20MUST.20.60inhabited.60.3F/near/477905312)	2024-10-23 06:32:11 +00:00