Goal:
    G : t  HI : invariants
  ============================
   (forall x : VSet.elt,
    (VSet.In x (V G) -> lsp x x = Some 0) <->
    (VSet.In x (V G) ->
     match lsp x x with
     | Some 0 => true
     | _ => false
     end = true))


DEBUG:Going to execute:
intro x
DEBUG LTAC Evaluated term: iff_forall