From 5f99e5775aec0f2b14b8c277816ca20622993314 Mon Sep 17 00:00:00 2001
From: Roger-luo <hiroger@qq.com>
Date: Wed, 24 Oct 2018 15:40:10 -0400
Subject: [PATCH 1/3] fix #458

---
 src/tracker/array.jl | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/tracker/array.jl b/src/tracker/array.jl
index c75b5c1c..f13feb77 100644
--- a/src/tracker/array.jl
+++ b/src/tracker/array.jl
@@ -82,6 +82,17 @@ Base.getindex(xs::TrackedArray, i...) = track(getindex, xs, i...)
   end
 end
 
+Base.view(x::TrackedArray, inds...) = track(Base.view, x, inds...)
+
+@grad function view(x::AbstractArray, inds...)
+    view(data(x), inds...), function (Δ)
+        grad_output = fill!(similar(data(x)), 0)
+        subgrad = view(grad_output, inds...)
+        setindex!(subgrad, Δ, :)
+        (grad_output, map(_->nothing, inds)...)
+    end
+end
+
 Base.:-(xs::TrackedArray) = track(-, xs)
 
 @grad -(xs) = -data(xs), Δ -> (-Δ,)

From a3cda9016c48ee19367e7732bdb560b90ef5fe5b Mon Sep 17 00:00:00 2001
From: Roger-luo <hiroger@qq.com>
Date: Thu, 25 Oct 2018 13:48:33 -0400
Subject: [PATCH 2/3] apply Mike's change

---
 src/tracker/array.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/tracker/array.jl b/src/tracker/array.jl
index f13feb77..9c89b5f6 100644
--- a/src/tracker/array.jl
+++ b/src/tracker/array.jl
@@ -86,9 +86,9 @@ Base.view(x::TrackedArray, inds...) = track(Base.view, x, inds...)
 
 @grad function view(x::AbstractArray, inds...)
     view(data(x), inds...), function (Δ)
-        grad_output = fill!(similar(data(x)), 0)
+        grad_output = zero(x)
         subgrad = view(grad_output, inds...)
-        setindex!(subgrad, Δ, :)
+        subgrad[:] = Δ
         (grad_output, map(_->nothing, inds)...)
     end
 end

From e5d58699e6255ed662104af13f3215dfa922795b Mon Sep 17 00:00:00 2001
From: Roger-luo <hiroger@qq.com>
Date: Fri, 26 Oct 2018 14:06:17 -0400
Subject: [PATCH 3/3] fix and add test

---
 src/tracker/array.jl | 4 ++--
 test/tracker.jl      | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/tracker/array.jl b/src/tracker/array.jl
index 9c89b5f6..a93ca423 100644
--- a/src/tracker/array.jl
+++ b/src/tracker/array.jl
@@ -88,8 +88,8 @@ Base.view(x::TrackedArray, inds...) = track(Base.view, x, inds...)
     view(data(x), inds...), function (Δ)
         grad_output = zero(x)
         subgrad = view(grad_output, inds...)
-        subgrad[:] = Δ
-        (grad_output, map(_->nothing, inds)...)
+        subgrad[:] = data(Δ)
+        (nobacksies(:view, grad_output), map(_->nothing, inds)...)
     end
 end
 
diff --git a/test/tracker.jl b/test/tracker.jl
index 1f5f6240..baa65cce 100644
--- a/test/tracker.jl
+++ b/test/tracker.jl
@@ -33,6 +33,11 @@ gradtest(f, dims...) = gradtest(f, rand.(Float64, dims)...)
 @test gradtest(Flux.crossentropy, rand(5,5), rand(5, 5))
 
 @test gradtest(x -> x', rand(5))
+
+@testset "indexing & slicing" begin
+  gradtest(x->view(x, 1:2, 1:2), rand(4, 4))
+end
+
 function promotiontest(f, A, B, C)
   r0 = f(A, B, C)
   r1 = f(param(A), B, C)