From d1f499309979fb53f4fa6d791cbfac803431579d Mon Sep 17 00:00:00 2001
From: Corey Farwell <coreyf@rwell.org>
Date: Sat, 20 May 2017 11:47:51 -0400
Subject: [PATCH] Add basic Unstable Book entry for `catch_expr`.

---
 .../src/language-features/catch-expr.md       | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/doc/unstable-book/src/language-features/catch-expr.md b/src/doc/unstable-book/src/language-features/catch-expr.md
index 44eb2a6dd4fd..fbd213dca569 100644
--- a/src/doc/unstable-book/src/language-features/catch-expr.md
+++ b/src/doc/unstable-book/src/language-features/catch-expr.md
@@ -5,3 +5,26 @@ The tracking issue for this feature is: [#31436]
 [#31436]: https://github.com/rust-lang/rust/issues/31436
 
 ------------------------
+
+The `catch_expr` feature adds support for a `catch` expression. The `catch`
+expression creates a new scope one can use the `?` operator in.
+
+```rust
+#![feature(catch_expr)]
+
+use std::num::ParseIntError;
+
+let result: Result<i32, ParseIntError> = do catch {
+    Ok("1".parse::<i32>()?
+        + "2".parse::<i32>()?
+        + "3".parse::<i32>()?)
+};
+assert_eq!(result, Ok(6));
+
+let result: Result<i32, ParseIntError> = do catch {
+    Ok("1".parse::<i32>()?
+        + "foo".parse::<i32>()?
+        + "3".parse::<i32>()?)
+};
+assert!(result.is_err());
+```