From 6afecc37e33713de6b372e4bfa9c348f9de4aab6 Mon Sep 17 00:00:00 2001
From: Brian Anderson <banderson@mozilla.com>
Date: Fri, 28 Oct 2011 16:18:16 -0700
Subject: [PATCH] Document the nullary-variant period in alt patterns

---
 doc/rust.texi | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/doc/rust.texi b/doc/rust.texi
index 82b7f1d429c1..04abd97fa557 100644
--- a/doc/rust.texi
+++ b/doc/rust.texi
@@ -3396,12 +3396,21 @@ alt x @{
     cons(10, _) @{
         process_ten();
     @}
+    nil. @{
+        ret;
+    @}
     _ @{
         fail;
     @}
 @}
 @end example
 
+Note in the above example that @code{nil} is followed by a period. This is
+required syntax for pattern matching a nullary tag variant, to distingush the
+variant @code{nil} from a binding to variable @code{nil}. Without the period
+the value of @code{x} would be bound to variable @code{nil} and the compiler
+would issue an error about the final wildcard case being unreachable.
+
 Multiple alternative patterns may be joined with the @code{|} operator.  A
 range of values may be specified with @code{to}.  For example: