substvars2.hlean:11:2: proof state
A B : Type,
a : A,
b : list B,
h₁ : A = list B,
h₂ : eq.rec_on h₁ a = list.nil B,
h₄ : 0 + 1 = 0 + 2
⊢ b = eq.rec_on h₁ a × 0 = 1