From 140de09c68d2697c6b787873caf0b4445edb6374 Mon Sep 17 00:00:00 2001
From: Twan Koolen <koolen.twan@gmail.com>
Date: Thu, 21 Dec 2017 09:51:32 +0100
Subject: [PATCH] [ci skip]

Improve broadcast! extension docs.
---
 doc/src/manual/interfaces.md | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/doc/src/manual/interfaces.md b/doc/src/manual/interfaces.md
index 19c83f222a681..bf4d4ed09df07 100644
--- a/doc/src/manual/interfaces.md
+++ b/doc/src/manual/interfaces.md
@@ -618,3 +618,12 @@ broadcast!(f, dest, ::MyBroadcastStyle, As...)
 ```
 
 Note the lack of bounds on `f`, `dest`, and `As...`.
+
+Third, simultaneously specializing on both the type of `dest` and the `BroadcastStyle` is fine. In this case,
+it is also allowed to specialize on the types of the source arguments (`As...`). For example, these method signatures are OK:
+
+```julia
+broadcast!(f, dest::DestType, ::MyBroadcastStyle, As...)
+broadcast!(f, dest::DestType, ::MyBroadcastStyle, As::AbstractArray...)
+broadcast!(f, dest::DestType, ::Broadcast.Scalar, As::Number...)
+```