Fix indexing + add regression test (#140)

src/sensitivities/indexing.jl

@@ -11,7 +11,7 @@ function ∇(Ā, ::typeof(getindex), ::Type{Arg{1}}, p, y, ȳ, A, inds...)
     return Ā
 end
 function ∇(Ā, ::typeof(getindex), ::Type{Arg{1}}, p, y::AbstractArray, ȳ::AbstractArray, A, inds...)
-    Ā[inds...] .+= reshape(ȳ, size(y)...)
+    @views Ā[inds...] .+= reshape(ȳ, size(y)...)
     return Ā
 end
 function ∇(::typeof(getindex), ::Type{Arg{1}}, p, y, ȳ, A, inds...)

test/sensitivities/indexing.jl

@@ -1,15 +1,22 @@
 @testset "Indexing" begin
-    let
+    @testset "Int" begin
         leaf = Leaf(Tape(), 5 * [1, 1, 1, 1, 1])
         y = getindex(leaf, 1)
         @test unbox(y) == 5
         @test ∇(y, one(unbox(y)))[leaf] == [1, 0, 0, 0, 0]
     end
 
-    let
+    @testset "Vector" begin
         x = Leaf(Tape(), 10 * [1, 1, 1])
         y = x[2:3]
         @test unbox(y) == [10, 10]
         @test ∇(y, oneslike(unbox(y)))[x] == [0, 1, 1]
     end
+
+    @testset "Overlapping indices (#139)" begin
+        x = Leaf(Tape(), 10 * [1, 1, 1])
+        y = x[[2, 3, 3]]
+        @test unbox(y) == [10, 10, 10]
+        @test ∇(y, oneslike(unbox(y)))[x] == [0, 1, 2]
+    end
 end