Anomaly in parsing inputs

[patrick-nicodemus]

I am probably just using this wrong but maybe we could get something better than "Assertion failed" for this error message?

Elpi Tactic abc. 
Elpi Accumulate lp:{{ 
  solve G GL.
}}.

Goal forall (x : nat), x = x.
Proof.
  intros.
  elpi abc ltac_term:(x).

Anomaly "File "src/rocq_elpi_arg_HOAS.ml", line 1107, characters 70-76: Assertion failed."
Please report at http://rocq-prover.org/bugs/.

the tutorial says ltac_term:(v) (for v of type constr or open_constr or uconstr or hyp), and x is a hyp so not sure what i'm doing wrong.

[patrick-nicodemus]

Tactic Notation "xyz" hyp(t) :=
  elpi abc ltac_term:(t).

Goal forall (x : nat), x = x.
Proof.
  intros.
  xyz x.
  (*  The reference xyz was not found in the current environment. *)

I fully acknowledge that this is just beginner error but it's not clear to me how to use this.