From a42326ffc920f23d62bcbb7589396a40b79c93a6 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Mon, 17 May 2021 15:55:01 +0100
Subject: [PATCH] if_let: Provide the logically-necessary fourth case

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 base/misc.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/base/misc.rs b/base/misc.rs
index 66c98fff..b4cb57cd 100644
--- a/base/misc.rs
+++ b/base/misc.rs
@@ -91,6 +91,14 @@ macro_rules! if_let {
       _ => { $($otherwise)* },
     };
   };
+  { $($variant:ident)::+ {$binding:ident} = $input:expr;
+    match $($otherwise:tt)*
+  } => {
+    let $binding = match $input {
+      $($variant)::+ { $binding } => $binding,
+      $($otherwise)*,
+    };
+  };
 }
 
 #[ext(pub, name=DebugExt)]
-- 
2.30.2