matchVarNames.lean:13:29-13:30: error: don't know how to synthesize placeholder
context:
α✝ : Type
β : α✝ → Type u_1
is : List α✝
i i✝ : α✝
is✝ : List α✝
a : β i✝
as : HList β is✝
h : Member i is✝
⊢ Member i is✝