congr! 1
X : DefName
xs : List VarName
σ σ' : VarName → VarName
h1 : ∀ v ∈ xs, σ v = σ' v
⊢ def_ X (List.map σ xs) = def_ X (List.map σ' xs)
case h.e'_2
X : DefName
xs : List VarName
σ σ' : VarName → VarName
h1 : ∀ v ∈ xs, σ v = σ' v
⊢ List.map σ xs = List.map σ' xs