Goal:
    A : Type  x : A  y : A  a : A  l2 : list A  H : [x] = a :: l2 ++ [y]
  ============================
   ([] = a :: l2 ∧ x = y)


DEBUG:Going to execute:
inversion H; subst; clear H
Level 1: evaluation returns
inversion H; subst; clear H
where
H := H
of type
constr of type tacvalue