From 20c75d84b7aa5e8e71657978b49d9a2c45103470 Mon Sep 17 00:00:00 2001
From: Sacha Verweij <sacha@stanford.edu>
Date: Sun, 25 Dec 2016 14:46:36 -0800
Subject: [PATCH] Make broadcast!(f, A) populate A via independent f() calls
 rather than fill!(A, f()).

---
 base/sysimg.jl    | 2 +-
 test/broadcast.jl | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/base/sysimg.jl b/base/sysimg.jl
index 60c677b072df8..b43b7aa1562e4 100644
--- a/base/sysimg.jl
+++ b/base/sysimg.jl
@@ -78,7 +78,7 @@ Symbol(x...) = Symbol(string(x...))
 # specific array types etc.
 #  --Here, just define fallback routines for broadcasting with no arguments
 broadcast(f) = f()
-broadcast!(f, X::AbstractArray) = fill!(X, f())
+broadcast!(f, X::AbstractArray) = (@inbounds for I in eachindex(X); X[I] = f(); end; X)
 
 # array structures
 include("array.jl")
diff --git a/test/broadcast.jl b/test/broadcast.jl
index c7b12a74fadcd..314a94844c2bf 100644
--- a/test/broadcast.jl
+++ b/test/broadcast.jl
@@ -373,3 +373,6 @@ end
 @test (+).(Ref(1), Ref(2)) == fill(3)
 @test (+).([[0,2], [1,3]], [1,-1]) == [[1,3], [0,2]]
 @test (+).([[0,2], [1,3]], Ref{Vector{Int}}([1,-1])) == [[1,1], [2,2]]
+
+# Check that broadcast!(f, A) populates A via independent calls to f (#12277, #19722).
+@test let z = 1; A = broadcast!(() -> z += 1, zeros(2)); A[1] != A[2]; end