Use let-in aware prod_applist_assum in dtauto and firstorder.

Fixes #6490.
`prod_applist_assum` is copied from `kernel/term.ml` to `engine/termops.ml`,
and adjusted to work with econstr.

This change uncovered a bug in `Hipattern.match_with_nodep_ind`, where
`has_nodep_prod_after` counts both products and let-ins, but was only
being passed `mib.mind_nparams`, which does not count let-ins.
Replaced with (Context.Rel.length mib.mind_params_ctxt).

1 files changed, 12 insertions, 0 deletions

diff --git a/engine/termops.ml b/engine/termops.ml
index a71bdff31..40b3d0d8b 100644
--- a/engine/termops.ml
+++ b/engine/termops.ml
@@ -1463,6 +1463,18 @@ let prod_applist sigma c l =
     | _ -> anomaly (Pp.str "Not enough prod's.") in
   app [] c l
 
+let prod_applist_assum sigma n c l =
+  let open EConstr in
+  let rec app n subst c l =
+    if Int.equal n 0 then
+      if l == [] then Vars.substl subst c
+      else anomaly (Pp.str "Not enough arguments.")
+    else match EConstr.kind sigma c, l with
+    | Prod(_,_,c), arg::l -> app (n-1) (arg::subst) c l
+    | LetIn(_,b,_,c), _ -> app (n-1) (Vars.substl subst b::subst) c l
+    | _ -> anomaly (Pp.str "Not enough prod/let's.") in
+  app n [] c l
+
 (* Combinators on judgments *)
 
 let on_judgment f j = { uj_val = f j.uj_val; uj_type = f j.uj_type }