patch 7.4.2045
Problem:    Memory leak when using a function callback.
Solution:   Don't save the function name when it's in the partial.
diff --git a/src/channel.c b/src/channel.c
index 90ef974..ae5bdf2 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -1122,7 +1122,12 @@
 {
     free_callback(*cbp, *pp);
     if (callback != NULL && *callback != NUL)
-	*cbp = vim_strsave(callback);
+    {
+	if (partial != NULL)
+	    *cbp = partial->pt_name;
+	else
+	    *cbp = vim_strsave(callback);
+    }
     else
 	*cbp = NULL;
     *pp = partial;