AbstractSet is functor

Project.toml

@@ -1,7 +1,7 @@
 name = "Functors"
 uuid = "d9f16b24-f501-4c13-a1f2-28368ffc5196"
 authors = ["Mike J Innes <mike.j.innes@gmail.com>"]
-version = "0.5.2"
+version = "0.5.3"
 
 [deps]
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"

src/base.jl

@@ -34,6 +34,8 @@ end
   functor(::Type{<:Base.Fix{N}}, x) where N = (; x.f, x.x), y -> Base.Fix{N}(y.f, y.x)
 end
 
+# Otherwise Base.Set are treated as Dict{K,Nothing}
+functor(::Type{S}, x) where {S<:AbstractSet} = collect(x), constructorof(S)
 
 ###
 ### Array wrappers

test/base.jl

@@ -49,6 +49,14 @@ end
     @test fmap(sqrt, Base.Fix2(/, 4); exclude)(10) == 5.0
 end
 
+@testset "Set" begin
+  s = Set([4, 9])
+  (xs, rec) = Functors.functor(s)
+  @test issetequal(xs, s)
+  @test rec(xs) == s
+  @test fmap(sqrt, s) == rec(map(sqrt, xs)) == Set([2, 3])
+end
+
 @testset "BroadcastFunction" begin
   f = Bar(3.3)
   bf = Base.Broadcast.BroadcastFunction(f)
@@ -213,6 +221,15 @@ end
   @test od2[2] == 4
 end
 
+@testset "AbstractSet is functor" begin
+  os = OrderedSet([1, 2])
+  @test !Functors.isleaf(os)
+  os2 = fmap(x -> 2x, os)
+  @test os2 isa OrderedSet
+  @test os2[1] == 2
+  @test os2[2] == 4
+end
+
 @testset "Types are leaves" begin
   @test Functors.isleaf(Int)
   @test Functors.isleaf(Array)

test/runtests.jl

@@ -2,7 +2,7 @@ using Functors, Test
 using Zygote
 using LinearAlgebra
 using StaticArrays
-using OrderedCollections: OrderedDict
+using OrderedCollections: OrderedDict, OrderedSet
 using Measurements: ±
 
 @testset "Functors.jl" begin