theorem tr_respects :
    Respects (TM1.step M) (TM0.step (tr M)) fun (c₁ : Cfg₁) (c₂ : Cfg₁₀) ↦ trCfg M c₁ = c₂ :=
  fun_respects.2 fun ⟨l₁, v, T⟩ ↦ by
    cases' l₁ with l₁; · exact rfl
    simp only [trCfg, TM1.step, FRespects, Option.map]
    induction' M l₁ with _ _ IH _ _ IH _ _ IH generalizing v T
    case move _ _ IH => exact TransGen.head rfl (IH _ _)
    

Proof state:
case some.write
Γ : Type u_1
inst✝² : Inhabited Γ
Λ : Type u_2
inst✝¹ : Inhabited Λ
σ : Type u_3
inst✝ : Inhabited σ
M : Λ → Stmt₁
x✝ : Cfg₁
l₁ : Λ
a✝¹ : Γ → σ → Γ
a✝ : Stmt₁
IH :
  ∀ (v : σ) (T : Tape Γ),
    Reaches₁ (TM0.step (tr M)) { q := (some a✝, v), Tape := T }
      {
        q :=
          (match (TM1.stepAux a✝ v T).l with
            | some x => some (M x)
            | none => none,
            (TM1.stepAux a✝ v T).var),
        Tape := (TM1.stepAux a✝ v T).Tape }
v : σ
T : Tape Γ
⊢ Reaches₁ (TM0.step (tr M)) { q := (some (TM1.Stmt.write a✝¹ a✝), v), Tape := T }
    {
      q :=
        (match (TM1.stepAux (TM1.Stmt.write a✝¹ a✝) v T).l with
          | some x => some (M x)
          | none => none,
          (TM1.stepAux (TM1.Stmt.write a✝¹ a✝) v T).var),
      Tape := (TM1.stepAux (TM1.Stmt.write a✝¹ a✝) v T).Tape }
case some.load
Γ : Type u_1
inst✝² : Inhabited Γ
Λ : Type u_2
inst✝¹ : Inhabited Λ
σ : Type u_3
inst✝ : Inhabited σ
M : Λ → Stmt₁
x✝ : Cfg₁
l₁ : Λ
a✝¹ : Γ → σ → σ
a✝ : Stmt₁
IH :
  ∀ (v : σ) (T : Tape Γ),
    Reaches₁ (TM0.step (tr M)) { q := (some a✝, v), Tape := T }
      {
        q :=
          (match (TM1.stepAux a✝ v T).l with
            | some x => some (M x)
            | none => none,
            (TM1.stepAux a✝ v T).var),
        Tape := (TM1.stepAux a✝ v T).Tape }
v : σ
T : Tape Γ
⊢ Reaches₁ (TM0.step (tr M)) { q := (some (TM1.Stmt.load a✝¹ a✝), v), Tape := T }
    {
      q :=
        (match (TM1.stepAux (TM1.Stmt.load a✝¹ a✝) v T).l with
          | some x => some (M x)
          | none => none,
          (TM1.stepAux (TM1.Stmt.load a✝¹ a✝) v T).var),
      Tape := (TM1.stepAux (TM1.Stmt.load a✝¹ a✝) v T).Tape }
case some.branch
Γ : Type u_1
inst✝² : Inhabited Γ
Λ : Type u_2
inst✝¹ : Inhabited Λ
σ : Type u_3
inst✝ : Inhabited σ
M : Λ → Stmt₁
x✝ : Cfg₁
l₁ : Λ
a✝² : Γ → σ → Bool
a✝¹ a✝ : Stmt₁
a_ih✝¹ :
  ∀ (v : σ) (T : Tape Γ),
    Reaches₁ (TM0.step (tr M)) { q := (some a✝¹, v), Tape := T }
      {
        q :=
          (match (TM1.stepAux a✝¹ v T).l with
            | some x => some (M x)
            | none => none,
            (TM1.stepAux a✝¹ v T).var),
        Tape := (TM1.stepAux a✝¹ v T).Tape }
a_ih✝ :
  ∀ (v : σ) (T : Tape Γ),
    Reaches₁ (TM0.step (tr M)) { q := (some a✝, v), Tape := T }
      {
        q :=
          (match (TM1.stepAux a✝ v T).l with
            | some x => some (M x)
            | none => none,
            (TM1.stepAux a✝ v T).var),
        Tape := (TM1.stepAux a✝ v T).Tape }
v : σ
T : Tape Γ
⊢ Reaches₁ (TM0.step (tr M)) { q := (some (TM1.Stmt.branch a✝² a✝¹ a✝), v), Tape := T }
    {
      q :=
        (match (TM1.stepAux (TM1.Stmt.branch a✝² a✝¹ a✝) v T).l with
          | some x => some (M x)
          | none => none,
          (TM1.stepAux (TM1.Stmt.branch a✝² a✝¹ a✝) v T).var),
      Tape := (TM1.stepAux (TM1.Stmt.branch a✝² a✝¹ a✝) v T).Tape }
case some.goto
Γ : Type u_1
inst✝² : Inhabited Γ
Λ : Type u_2
inst✝¹ : Inhabited Λ
σ : Type u_3
inst✝ : Inhabited σ
M : Λ → Stmt₁
x✝ : Cfg₁
l₁ : Λ
a✝ : Γ → σ → Λ
v : σ
T : Tape Γ
⊢ Reaches₁ (TM0.step (tr M)) { q := (some (TM1.Stmt.goto a✝), v), Tape := T }
    {
      q :=
        (match (TM1.stepAux (TM1.Stmt.goto a✝) v T).l with
          | some x => some (M x)
          | none => none,
          (TM1.stepAux (TM1.Stmt.goto a✝) v T).var),
      Tape := (TM1.stepAux (TM1.Stmt.goto a✝) v T).Tape }
case some.halt
Γ : Type u_1
inst✝² : Inhabited Γ
Λ : Type u_2
inst✝¹ : Inhabited Λ
σ : Type u_3
inst✝ : Inhabited σ
M : Λ → Stmt₁
x✝ : Cfg₁
l₁ : Λ
v : σ
T : Tape Γ
⊢ Reaches₁ (TM0.step (tr M)) { q := (some TM1.Stmt.halt, v), Tape := T }
    {
      q :=
        (match (TM1.stepAux TM1.Stmt.halt v T).l with
          | some x => some (M x)
          | none => none,
          (TM1.stepAux TM1.Stmt.halt v T).var),
      Tape := (TM1.stepAux TM1.Stmt.halt v T).Tape }

Next tactic:
case write _ _ IH => exact TransGen.head rfl (IH _ _)