left
case pos
v x : VarName
phi : Formula
phi_ih : ∀ (binders : Finset VarName), v ∉ binders → fastAdmitsAux v v binders phi
binders : Finset VarName
h1 : v ∉ binders
c1 : v = x
⊢ v = x ∨ fastAdmitsAux v v (binders ∪ {x}) phi
case pos.h
v x : VarName
phi : Formula
phi_ih : ∀ (binders : Finset VarName), v ∉ binders → fastAdmitsAux v v binders phi
binders : Finset VarName
h1 : v ∉ binders
c1 : v = x
⊢ v = x