From fb25587a879433b8e475bc7b1fad918ef43fb709 Mon Sep 17 00:00:00 2001
From: Nick Levine <ndl@ravenbrook.com>
Date: Sun, 26 May 2013 13:16:42 +0100
Subject: [PATCH] (Bug #308954: Wrong error from methodless generic function)

no-applicable-method will be called when a methodless gf is
invoked. Check whether there are any methods and craft the error
message appropriately.

(I dithered about whether the message could tell you that you also got
the argument count wrong; in the end, I decided that getting a less
misleading message is good enough. I also dithered about whether or
not this error should fire a call to no-applicable-method; I concluded
that there isn't any applicable method -- there are no methods at all.)
---
 src/pcl/braid.lisp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/pcl/braid.lisp b/src/pcl/braid.lisp
index ce6bbc1..b043b4f 100644
--- a/src/pcl/braid.lisp
+++ b/src/pcl/braid.lisp
@@ -711,8 +711,13 @@
 (setq **boot-state** 'braid)

 (defmethod no-applicable-method (generic-function &rest args)
-  (error "~@<There is no applicable method for the generic function ~2I~_~S~
+  (error "~@<There ~a for the generic function ~2I~_~S~
           ~I~_when called with arguments ~2I~_~S.~:>"
+         (if (if (early-gf-p generic-function)
+                 (early-gf-methods generic-function)
+                 (safe-generic-function-methods generic-function))
+             "is no applicable method"
+             "are no methods at all")
          generic-function
          args))

--
1.8.2.1