From b0b4a482965d68dbd4083968f78f66b9122f4aac Mon Sep 17 00:00:00 2001
From: Simeon Schaub <simeondavidschaub99@gmail.com>
Date: Sat, 3 Apr 2021 20:43:43 +0200
Subject: [PATCH] fix inconsistent BroadcastFunction behavior (#40330)

fixes #40309
---
 base/broadcast.jl | 8 +++++++-
 test/broadcast.jl | 4 ++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/base/broadcast.jl b/base/broadcast.jl
index de3263a64011b..c6d079d318acf 100644
--- a/base/broadcast.jl
+++ b/base/broadcast.jl
@@ -1300,7 +1300,13 @@ macro __dot__(x)
     esc(__dot__(x))
 end
 
-@inline broadcasted_kwsyntax(f, args...; kwargs...) = broadcasted((args...)->f(args...; kwargs...), args...)
+@inline function broadcasted_kwsyntax(f, args...; kwargs...)
+    if isempty(kwargs) # some BroadcastStyles dispatch on `f`, so try to preserve its type
+        return broadcasted(f, args...)
+    else
+        return broadcasted((args...) -> f(args...; kwargs...), args...)
+    end
+end
 @inline function broadcasted(f, args...)
     args′ = map(broadcastable, args)
     broadcasted(combine_styles(args′...), f, args′...)
diff --git a/test/broadcast.jl b/test/broadcast.jl
index 6e97d609a42b0..28c56b2c2e636 100644
--- a/test/broadcast.jl
+++ b/test/broadcast.jl
@@ -1015,3 +1015,7 @@ end
         @test a_ == dropdims(a .* c, dims=(findall(==(1), size(c))...,))
     end
 end
+
+# issue 40309
+@test Base.broadcasted_kwsyntax(+, [1], [2]) isa Broadcast.Broadcasted{<:Any, <:Any, typeof(+)}
+@test Broadcast.BroadcastFunction(+)(2:3, 2:3) === 4:2:6