fix GNNChain restructure bug

Author: mplemay

src/layers/basic.jl

@@ -115,6 +115,7 @@ end
     Base.iterate, Base.lastindex, Base.keys
 
 Flux.functor(::Type{<:GNNChain}, c) = c.layers, ls -> GNNChain(ls...)
+Flux.functor(::Type{<:GNNChain}, c::Tuple) = c, ls -> GNNChain(ls...)
 
 # input from graph
 applylayer(l, g::GNNGraph) = GNNGraph(g, ndata=l(node_features(g)))

test/layers/basic.jl

@@ -64,5 +64,11 @@
         wg = WithGraph(model, g, traingraph=true)
         @test length(Flux.params(wg)) == length(Flux.params(model)) + length(Flux.params(g))
     end
+
+    @testset "Flux restructure" begin
+        chain = GNNChain(GraphConv(2=>2))
+        params, restructure = Flux.destructure(chain)
+        restructure(params)
+    end
 end