From 6ba374c62baa43e56f8d56dbbf59d9952d502143 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Fri, 26 Nov 2021 17:11:35 +0100
Subject: [PATCH 1/2] ENHANCED: use '$skip_max_list'/4 for fast list tests in
 can_be/2 and must_be/2

This also (partially) addresses #1108.
---
 src/lib/error.pl | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/src/lib/error.pl b/src/lib/error.pl
index d6bf8708..749ad04e 100644
--- a/src/lib/error.pl
+++ b/src/lib/error.pl
@@ -79,9 +79,12 @@ character(C) :-
         atom(C),
         atom_length(C, 1).
 
-ilist(V) :- var(V), instantiation_error(must_be/2).
-ilist([]).
-ilist([_|Ls]) :- ilist(Ls).
+ilist(Ls) :-
+        '$skip_max_list'(_, -1, Ls, Rs),
+        (   var(Rs) ->
+            instantiation_error(must_be/2)
+        ;   Rs == []
+        ).
 
 type(type).
 type(integer).
@@ -120,10 +123,11 @@ can_(chars, Ls)     :- '$is_partial_string'(Ls).
 can_(list, Term)    :- list_or_partial_list(Term).
 can_(boolean, Term) :- boolean(Term).
 
-list_or_partial_list(Var) :- var(Var).
-list_or_partial_list([]).
-list_or_partial_list([_|Ls]) :-
-        list_or_partial_list(Ls).
+list_or_partial_list(Ls) :-
+        '$skip_max_list'(_, -1, Ls, Rs),
+        (   var(Rs) -> true
+        ;   Rs == []
+        ).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Shorthands for throwing ISO errors.

From 803e120a5108048bbab10872b4f2933f113c361b Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Fri, 26 Nov 2021 17:11:51 +0100
Subject: [PATCH 2/2] use must_be(list, ...) earlier, since it is now faster

---
 src/lib/error.pl | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/lib/error.pl b/src/lib/error.pl
index 749ad04e..d5827495 100644
--- a/src/lib/error.pl
+++ b/src/lib/error.pl
@@ -47,13 +47,13 @@ must_be_(integer, Term) :- check_(integer, integer, Term).
 must_be_(atom, Term)    :- check_(atom, atom, Term).
 must_be_(character, T)  :- check_(error:character, character, T).
 must_be_(chars, Ls) :-
-        (   ground(Ls), '$is_partial_string'(Ls) ->
+        must_be(list, Ls),
+        (   '$is_partial_string'(Ls) ->
             % The expected case (success) uses a very fast test.
             % We cannot use partial_string/1 from library(iso_ext),
             % because that library itself imports library(error).
             true
-        ;   must_be(list, Ls),
-            all_characters(Ls)
+        ;   all_characters(Ls)
         ).
 must_be_(list, Term)    :- check_(error:ilist, list, Term).
 must_be_(type, Term)    :- check_(error:type, type, Term).