From 31218add95ce6c94234be2364e7ebbd276101ab9 Mon Sep 17 00:00:00 2001
From: Eduardo Pinho <enet4mikeenet@gmail.com>
Date: Sun, 14 Jan 2018 21:23:19 +0000
Subject: [PATCH] Include note for implementers of AsPrimitive

---
 src/cast.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/cast.rs b/src/cast.rs
index 9e6974f..2d7fe19 100644
--- a/src/cast.rs
+++ b/src/cast.rs
@@ -454,6 +454,9 @@ impl<T: NumCast> NumCast for Wrapping<T> {
 
 /// A generic interface for casting between machine scalars with the
 /// `as` operator, which admits narrowing and precision loss.
+/// Implementers of this trait AsPrimitive should behave like a primitive
+/// numeric type (e.g. a newtype around another primitive), and the
+/// intended conversion must never fail.
 ///
 /// # Examples
 ///