fix FillArrays 0.10 compat

Project.toml

@@ -28,7 +28,8 @@ julia = "1"
 
 [extras]
 DiffTests = "de460e47-3fe3-5279-bb4a-814414816d5d"
+FillArrays = "1a297f60-69ca-5386-bcde-b61e274b549b"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["DiffTests", "Test"]
+test = ["DiffTests", "FillArrays", "Test"]

src/derivatives/broadcast.jl

@@ -85,17 +85,17 @@ function get_implementation(bc, f, T, args)
 end
 function Base.copy(_bc::Broadcasted{TrackedStyle})
     bc = remove_not_tracked(_bc)
-    flattened_bc = Broadcast.flatten(bc)
+    flattened_bc = Base.Broadcast.flatten(bc)
     untracked_bc = broadcast_rebuild(bc)
-    flattened_untracked_bc = Broadcast.flatten(untracked_bc)
     T = Core.Compiler.return_type(copy, Tuple{typeof(untracked_bc)})
-    f, args = flattened_untracked_bc.f, flattened_bc.args
+    f, args = flattened_bc.f, flattened_bc.args
     implementation = get_implementation(_bc, f, T, args)
     if implementation isa Val{:reversediff}
         return ∇broadcast(f, args...)
     elseif implementation isa Val{:tracker}
         return tracker_∇broadcast(f, args...)
     else
+        flattened_untracked_bc = Base.Broadcast.flatten(untracked_bc)
         style, axes = getstyle(flattened_untracked_bc), flattened_bc.axes
         return copy(Broadcasted{style, typeof(axes), typeof(f), typeof(args)}(f, args, axes))
     end

test/compat/CompatTests.jl

@@ -0,0 +1,13 @@
+module CompatTests
+
+using FillArrays, ReverseDiff, Test
+
+@test ReverseDiff.gradient(fill(2.0, 3)) do x
+  sum(abs2.(x .- Zeros(3)))
+end == fill(4.0, 3)
+
+@test ReverseDiff.gradient(fill(2.0, 3)) do x
+  sum(abs2.(x .- (1:3)))
+end == [2, 0, -2]
+
+end

test/runtests.jl

@@ -45,3 +45,7 @@ println("done (took $t seconds).")
 println("running ConfigTests...")
 t = @elapsed include(joinpath(TESTDIR, "api/ConfigTests.jl"))
 println("done (took $t seconds).")
+
+println("running CompatTests...")
+t = @elapsed include(joinpath(TESTDIR, "compat/CompatTests.jl"))
+println("done (took $t seconds).")