From 1952353e85acc8e960a43e25e0ebf0306b0b7359 Mon Sep 17 00:00:00 2001
From: Adam Chalmers <achalmers@cloudflare.com>
Date: Thu, 5 Sep 2019 20:22:14 -0500
Subject: [PATCH] Revert "Remove TryFrom due to destabilization"

This reverts commit 2a808e6a3d25a26702a4a4a08568904764ae1bea.
---
 src/SUMMARY.md                      |  1 +
 src/conversion/try_from_try_into.md | 45 +++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 src/conversion/try_from_try_into.md

diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index 6121054342..1969ed05a5 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -36,6 +36,7 @@
 
 - [Conversion](conversion.md)
     - [`From` and `Into`](conversion/from_into.md)
+    - [`TryFrom` and `TryInto`](conversion/try_from_try_into.md)
     - [To and from `String`s](conversion/string.md)
 
 - [Expressions](expression.md)
diff --git a/src/conversion/try_from_try_into.md b/src/conversion/try_from_try_into.md
new file mode 100644
index 0000000000..9e3242895b
--- /dev/null
+++ b/src/conversion/try_from_try_into.md
@@ -0,0 +1,45 @@
+# `TryFrom` and `TryInto`
+
+Similar to [`From` and `Into`][from-into], [`TryFrom`] and [`TryInto`] are
+generic traits for converting between types. Unlike `From`/`Into`, the
+`TryFrom`/`TryInto` traits are used for fallible conversions, and as such,
+return [`Result`]s.
+
+[from-into]: conversion/from_into.html
+[`TryFrom`]: https://doc.rust-lang.org/std/convert/trait.TryFrom.html
+[`TryInto`]: https://doc.rust-lang.org/std/convert/trait.TryInto.html
+[`Result`]: https://doc.rust-lang.org/std/result/enum.Result.html
+
+```rust
+use std::convert::TryFrom;
+use std::convert::TryInto;
+
+#[derive(Debug, PartialEq)]
+struct EvenNumber(i32);
+
+impl TryFrom<i32> for EvenNumber {
+    type Error = ();
+
+    fn try_from(value: i32) -> Result<Self, Self::Error> {
+        if value % 2 == 0 {
+            Ok(EvenNumber(value))
+        } else {
+            Err(())
+        }
+    }
+}
+
+fn main() {
+    // TryFrom
+
+    assert_eq!(EvenNumber::try_from(8), Ok(EvenNumber(8)));
+    assert_eq!(EvenNumber::try_from(5), Err(()));
+
+    // TryInto
+
+    let result: Result<EvenNumber, ()> = 8i32.try_into();
+    assert_eq!(result, Ok(EvenNumber(8)));
+    let result: Result<EvenNumber, ()> = 5i32.try_into();
+    assert_eq!(result, Err(()));
+}
+```