Add a test that `prod_applist_assum` reduces the right number of let-ins

1 files changed, 4 insertions, 1 deletions

diff --git a/engine/termops.mli b/engine/termops.mli
index 1f4c85054..a3559a693 100644
--- a/engine/termops.mli
+++ b/engine/termops.mli
@@ -165,7 +165,10 @@ val prod_applist : Evd.evar_map -> constr -> constr list -> constr
 (** In [prod_applist_assum n c args], [c] is supposed to have the
     form [∀Γ.c] with [Γ] of length [m] and possibly with let-ins; it
     returns [c] with the assumptions of [Γ] instantiated by [args] and
-    the local definitions of [Γ] expanded. *)
+    the local definitions of [Γ] expanded.
+    Note that [n] counts both let-ins and prods, while the length of [args]
+    only counts prods. In other words, varying [n] changes how many
+    trailing let-ins are expanded. *)
 val prod_applist_assum : Evd.evar_map -> int -> constr -> constr list -> constr
 
 (** Remove recursively the casts around a term i.e.