Merge pull request #1063 from FluxML/cl/pair

fix pair getfield pullback

src/lib/base.jl

@@ -118,23 +118,26 @@ end
 
 # named tuple
 @adjoint function pairs(t::NamedTuple{N}) where N
-    pairs_namedtuple(dx::NamedTuple) = (dx.data,)
-    function pairs_namedtuple(Δ::Dict)
-        t0 = map(zero, t)
-        for (idx, v) in Δ
-            t0 = NamedTuple{N}(Base.setindex((t0...,), v, idx))
-        end
-        return (t0,)
+
+  pairs_namedtuple_pullback(dx::NamedTuple) = (dx.data,)
+
+  function pairs_namedtuple_pullback(Δ::Dict)
+    t0 = map(zero, t)
+    for (idx, v) in Δ
+      t0 = NamedTuple{N}(Base.setindex((t0...,), v, idx))
     end
-    return pairs(t), pairs_namedtuple
+    return (t0,)
+  end
+
+  return pairs(t), pairs_namedtuple_pullback
 end
 
 @adjoint function Base.getfield(p::Pair, i::Int)
-    function pair_getfield(Δ)
-        f, s = i == 1 ? (Δ, zero(p[2])) : (zero(p[1]), Δ)
+    function pair_getfield_pullback(Δ)
+        f, s = i == 1 ? (Δ, nothing) : (nothing, Δ)
         return (first=f, second=s), nothing
     end
-    return getfield(p, i), pair_getfield
+    return getfield(p, i), pair_getfield_pullback
 end
 
 @adjoint Base.nameof(x::UnionAll) = nameof(x), _ -> (nothing,)

test/features.jl

@@ -424,17 +424,17 @@ end
 end
 
 mutable struct MyMutable
-    value::Float64
+  value::Float64
 end
 
 function foo!(m::MyMutable, x)
-    m.value = x
+  m.value = x
 end
 
 function baz(args)
-    m = MyMutable(0.)
-    foo!(m, args...)
-    m.value
+  m = MyMutable(0.)
+  foo!(m, args...)
+  m.value
 end
 
 let
@@ -449,13 +449,18 @@ end
 @test pullback(type_test)[1] == Complex{<:Real}
 
 @testset "Pairs" begin
-    @test (x->10*pairs((a=x, b=2))[1])'(100) === 10.0
-    @test (x->10*pairs((a=x, b=2))[2])'(100) === 0
-    foo(;kw...) = 1
-    @test gradient(() -> foo(a=1,b=2.0)) === ()
-
-    @test (x->10*(x => 2)[1])'(100) === 10.0
-    @test (x->10*(x => 2)[2])'(100) === 0
+  @test (x->10*pairs((a=x, b=2))[1])'(100) === 10.0
+  @test (x->10*pairs((a=x, b=2))[2])'(100) === 0
+  foo(;kw...) = 1
+  @test gradient(() -> foo(a=1,b=2.0)) === ()
+
+  @test (x->10*(x => 2)[1])'(100) === 10.0
+  @test (x->10*(x => 2)[2])'(100) === nothing
+
+  @test gradient(x-> (:x => x)[2], 17) == (1,)
+
+  d = Dict(:x=>1.0, :y=>3.0);
+  @test gradient(d -> Dict(:x => d[:x])[:x], d) == (Dict(:x => 1),)
 end
 
 # https://github.com/JuliaDiff/ChainRules.jl/issues/257