ext x'
ν : Type u_1
inst✝ : DecidableEq ν
τ : PropAssignment ν
x : ν
v v' : Bool
⊢ set (set τ x v) x v' = set τ x v'
case h
ν : Type u_1
inst✝ : DecidableEq ν
τ : PropAssignment ν
x : ν
v v' : Bool
x' : ν
⊢ set (set τ x v) x v' x' = set τ x v' x'