Goal:
  
  A : Type
  P : list A → A → Type
  d : A
  Γ : list A
  a : All_fold P Γ
  p : P Γ d
  b : All_fold P Γ
  p0 : P Γ d
  e : {| pr1 := a; pr2 := p |} = {| pr1 := b; pr2 := p0 |}
  ============================
   (noConfusionHom_All_fold_obligation_2 A P (d :: Γ) 
      (All_fold_cons P a p) (All_fold_cons P b p0)
      (noConfusionHom_All_fold_obligation_1 A P (d :: Γ)
         (All_fold_cons P a p) (All_fold_cons P b p0) e) = e)


DEBUG:Going to execute:
fun H =>
             match type of H with
             | ?R ?x ?y =>
                 let rhs := fresh in
                 set (rhs := y) in *; pattern sigma rhs; clearbody rhs;
                  destruct H; simpl
             end