case error _ =>
  rw [Hhead] at H; contradiction
α₁ σ₁ : Type
ε₁ : σ₁ → Type
δ₁ : Dialect α₁ σ₁ ε₁
α₂ σ₂ : Type
ε₂ : σ₂ → Type
δ₂ : Dialect α₂ σ₂ ε₂
α✝ σ✝ : Type
ε✝ : σ✝ → Type
Δ : Dialect α✝ σ✝ ε✝
S : Semantics Δ
head : TypedSSAVal Δ
tail : List (TypedSSAVal Δ)
env : SSAEnv Δ
r : List (TypedArg Δ)
resEnv : SSAEnv Δ
name : SSAVal
τ : MLIRType Δ
v : MLIRType.eval τ
headName : SSAVal
headτ : MLIRType Δ
H :
  (match TopM.get headτ headName env with
    | Except.error err => Except.error err
    | Except.ok v =>
      match
        mapM
          (fun x s =>
            match TopM.get x.snd x.fst s with
            | Except.error err => Except.error err
            | Except.ok v => Except.ok ({ fst := x.snd, snd := v.fst }, v.snd))
          tail v.snd with
      | Except.error err => Except.error err
      | Except.ok v_1 => Except.ok ({ fst := headτ, snd := v.fst } :: v_1.fst, v_1.snd)) =
    Except.ok (r, resEnv)
HInd :
  ∀ ⦃env : SSAEnv Δ⦄ ⦃r : List (TypedArg Δ)⦄ ⦃resEnv : SSAEnv Δ⦄,
    denoteOpArgs Δ tail env = Except.ok (r, resEnv) →
      ∀ ⦃name : SSAVal⦄,
        (∀ (a : SSAVal) (b : MLIRType Δ), (a, b) ∈ tail → ¬name = a) →
          ∀ (τ : MLIRType Δ) (v : MLIRType.eval τ),
            denoteOpArgs Δ tail (SSAEnv.set name τ v env) = Except.ok (r, SSAEnv.set name τ v resEnv)
Hname : ¬name = headName ∧ ∀ (a : SSAVal) (b : MLIRType Δ), (a, b) ∈ tail → ¬name = a
a✝ : String × SSAEnv Δ
Hhead : TopM.get headτ headName env = Except.error a✝
⊢ (match TopM.get headτ headName (SSAEnv.set name τ v env) with
    | Except.error err => Except.error err
    | Except.ok v =>
      match
        mapM
          (fun x s =>
            match TopM.get x.snd x.fst s with
            | Except.error err => Except.error err
            | Except.ok v => Except.ok ({ fst := x.snd, snd := v.fst }, v.snd))
          tail v.snd with
      | Except.error err => Except.error err
      | Except.ok v_1 => Except.ok ({ fst := headτ, snd := v.fst } :: v_1.fst, v_1.snd)) =
    Except.ok (r, SSAEnv.set name τ v resEnv)
no goals