From 9288717bed8eb383ed9347bc67a8b8b920defd07 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Thu, 1 Apr 2021 12:59:53 +0100
Subject: [PATCH] introduce if_let!

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 apitest/at-otter.rs |  2 +-
 base/misc.rs        | 10 ++++++++++
 base/prelude.rs     |  2 ++
 daemon/api.rs       |  2 +-
 4 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/apitest/at-otter.rs b/apitest/at-otter.rs
index 06c5ed7c..2a7ad118 100644
--- a/apitest/at-otter.rs
+++ b/apitest/at-otter.rs
@@ -371,7 +371,7 @@ pub fn update_update_pieces<PI:Idx>(
   let v = v.as_object().unwrap();
   let piece = v["piece"].as_str().unwrap();
   let p = pieces.iter_mut().find(|p| p.id == piece);
-  let p = if let Some(p) = p { p } else { return };
+  if_let!{ Some(p) = p; else return }
   let (op, d) = v["op"].as_object().unwrap().iter().next().unwrap();
 
   fn coord(j: &JsV) -> Pos {
diff --git a/base/misc.rs b/base/misc.rs
index 426c4ca9..b97369d9 100644
--- a/base/misc.rs
+++ b/base/misc.rs
@@ -64,3 +64,13 @@ pub fn space_rect_attrs(table_size: PosC<f64>) -> SvgAttrs {
     (Html::lit("height"), table_size.y().to_html()  ),
   ]
 }
+
+#[macro_export]
+macro_rules! if_let {
+  { $variant:ident($binding:pat) = $input:expr; else $($otherwise:tt)* } => {
+    let $binding = match $input {
+      $variant(y) => y,
+      _ => { $($otherwise)* },
+    };
+  }
+}
diff --git a/base/prelude.rs b/base/prelude.rs
index 143677e2..092409b0 100644
--- a/base/prelude.rs
+++ b/base/prelude.rs
@@ -32,3 +32,5 @@ pub use crate::geometry::{CoordinateOverflow, PosC};
 pub use crate::{hformat, hformat_as_display, hwrite};
 pub use crate::misc::default;
 pub use crate::misc::display_as_debug;
+
+pub use crate::if_let;
diff --git a/daemon/api.rs b/daemon/api.rs
index 902b36f1..412919cb 100644
--- a/daemon/api.rs
+++ b/daemon/api.rs
@@ -121,7 +121,7 @@ fn api_piece_op<O: op::Complex>(form: Json<ApiPiece<O>>)
   let _ = iplayers.byid(player)?;
   let gpl = gs.players.byid(player)?;
   let piece = vpiece_decode(gs, player, gpl, form.piece);
-  let piece = if let Some(piece) = piece { piece } else { return Ok(()) };
+  if_let!{ Some(piece) = piece; else return Ok(()) }
   let was_held = gs.pieces.get(piece).as_ref().map(|gpc| gpc.held);
   use ApiPieceOpError::*;
 
-- 
2.30.2