Goal:
    hd : A.t  tl : list A.t  hd' : A.t  tl' : list A.t  H : A.lt hd hd'
  ============================
   (forall x : t,
    {| pr1 := x; pr2 := x |} = {| pr1 := hd :: tl; pr2 := hd' :: tl' |} ->
    let H := CoreTactics.block in let H0 := CoreTactics.block in False)


DEBUG:Going to execute:
let H := fresh x in
           intro
           H
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.
Level 2: Backtrace:

The first hypothesis in the goal is not an equality.