Goal:
    hd : A.t  tl : list A.t  H : A.lt hd hd
  ============================
   (let H := CoreTactics.block in let H0 := CoreTactics.block in False)


DEBUG:Going to execute:
match goal with
           | hyp:context [ CoreTactics.block ]
             |- _ =>
                 cbn beta in hyp; eqns_specialize_eqs_block hyp;
                  cbn[eq_rect_r eq_rect] in hyp
           end