patch 8.1.1863: confusing error when using a builtin function as method
Problem: Confusing error when using a builtin function as method while it
does not support that.
Solution: Add a specific error message.
diff --git a/src/vim.h b/src/vim.h
index 1011be7..4107f6b 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2518,6 +2518,7 @@
#define ERROR_NONE 5
#define ERROR_OTHER 6
#define ERROR_DELETED 7
+#define ERROR_NOTMETHOD 8 // function cannot be used as a method
/* flags for find_name_end() */
#define FNE_INCL_BR 1 /* include [] in name */