Adds in-notes to LilyPond.

[lilypond.git] / scm / ly-syntax-constructors.scm

diff --git a/scm/ly-syntax-constructors.scm b/scm/ly-syntax-constructors.scm
index ebd0a605a0c37b1cf1844e84b55d059354ecee31..841ad92e97f203717bfaf9181b9795f0546cc1b2 100644 (file)
--- a/scm/ly-syntax-constructors.scm
+++ b/scm/ly-syntax-constructors.scm
@@ -44,22 +44,37 @@
 
 ;; Music function: Apply function and check return value.
 ;; args are in reverse order, rest may specify additional ones
+;;
+;; If args is not a proper list, an error has been flagged earlier
+;; and no fallback value had been available.  In this case,
+;; we don't call the function but rather return the general
+;; fallback.
 (define-ly-syntax (music-function parser loc fun args . rest)
   (let* ((sig (object-property fun 'music-function-signature))
         (pred (if (pair? (car sig)) (caar sig) (car sig)))
-        (m (apply fun parser loc (reverse! args rest))))
-    (if (pred m)
+        (good (proper-list? args))
+        (m (and good (apply fun parser loc (reverse! args rest)))))
+    (if (and good (pred m))
        (begin
          (if (ly:music? m)
              (set! (ly:music-property m 'origin) loc))
          m)
        (begin
-         (ly:parser-error parser
-                          (format #f (_ "~a function cannot return ~a")
-                                  (type-name pred) m)
-                          loc)
+         (if good
+             (ly:parser-error parser
+                              (format #f (_ "~a function cannot return ~a")
+                                      (type-name pred) m)
+                              loc))
          (and (pair? (car sig)) (cdar sig))))))
 
+(define-ly-syntax (argument-error parser location n pred arg)
+  (ly:parser-error
+   parser
+   (format #f
+          (_ "wrong type for argument ~a.  Expecting ~a, found ~s")
+          n (type-name pred) arg)
+   location))
+
 (define-ly-syntax-simple (void-music)
   (make-music 'Music))