X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=lily%2Fmusic-function-scheme.cc;h=93c7e0fbc4773cbc121ca45779b1c71db26c8c96;hb=ec5fe824131e5ac254c380acd420dca1d00b0db6;hp=f78a387336021f9c1166aec680b9fb1cae610e5c;hpb=f93e4199873c91ae32f0e84a610d14853dc379df;p=lilypond.git

diff --git a/lily/music-function-scheme.cc b/lily/music-function-scheme.cc
index f78a387336..93c7e0fbc4 100644
--- a/lily/music-function-scheme.cc
+++ b/lily/music-function-scheme.cc
@@ -20,11 +20,25 @@ LY_DEFINE (ly_make_music_function, "ly:make-music-function", 2, 0, 0,
            (SCM signature, SCM func),
            "Make a function to process music, to be used for the"
            " parser.  @var{func} is the function, and @var{signature}"
-           " describes its arguments.  @var{signature} is a list"
+           " describes its arguments.  @var{signature}'s cdr is a list"
            " containing either @code{ly:music?} predicates or other type"
-           " predicates.")
+           " predicates.  Its car is the syntax function to call.")
 {
-  LY_ASSERT_TYPE (ly_is_procedure, func, 1);
+  LY_ASSERT_TYPE (ly_is_list, signature, 1);
+  LY_ASSERT_TYPE (ly_is_procedure, func, 2);
+  int n = 0;
+  for (SCM p = signature; scm_is_pair (p); p = scm_cdr (p), ++n)
+    {
+      SCM proc = scm_car (p);
+      if (scm_is_pair (proc))
+        proc = scm_car (proc);
+      if (scm_is_false (scm_procedure_p (proc)))
+        {
+          scm_wrong_type_arg_msg ("music-function", n, p,
+                                  "music function predicate");
+        }
+    }
+
   return make_music_function (signature, func);
 }