Goal:
    A : Type  y : A  a : A  H2 : [] = [] ++ [y]
  ============================
   ([] = [a] ∧ a = y)


DEBUG:Going to execute:
PTRDEBUGTACinversion H; subst; clear H
DEBUG LTAC Evaluated term: H2
DEBUG LTAC Evaluated term: H2
DEBUG LTAC Evaluated term: H2
DEBUG LTAC Evaluated term: H2