From d4285efab2f0799bfeb26644eeb475eb755d1354 Mon Sep 17 00:00:00 2001
From: Will Tebbutt <wct23@cam.ac.uk>
Date: Mon, 7 Oct 2024 14:37:49 +0200
Subject: [PATCH] Handle `Union`s / `UnionAll`s of `Tuple`s in zero_rdata
 (#284)

* Handle unions and unionalls of tuples

* Bump patch

* Add comment

* Refine new tests

* Refine implementation

* Refine implementation further

* Add comment
---
 Project.toml          | 2 +-
 src/fwds_rvs_data.jl  | 1 +
 test/fwds_rvs_data.jl | 4 +++-
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/Project.toml b/Project.toml
index 4501ca07..edba62cb 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "Mooncake"
 uuid = "da2b9cff-9c12-43a0-ae48-6db2b0edb7d6"
 authors = ["Will Tebbutt, Hong Ge, and contributors"]
-version = "0.4.8"
+version = "0.4.9"
 
 [deps]
 ADTypes = "47edcb42-4c32-4615-8424-f2b9edc5f35b"
diff --git a/src/fwds_rvs_data.jl b/src/fwds_rvs_data.jl
index 16a8ce98..e506ee61 100644
--- a/src/fwds_rvs_data.jl
+++ b/src/fwds_rvs_data.jl
@@ -563,6 +563,7 @@ obtained from `P` alone.
     R == NoRData && return true
     isabstracttype(P) && return false
     (isconcretetype(P) || P <: Tuple) || return false
+    (P <: Tuple && !(P isa DataType)) && return false # catch Unions and UnionAlls
     (P <: Tuple && Base.datatype_fieldcount(P) === nothing) && return false
 
     # For general structs, just look at their fields.
diff --git a/test/fwds_rvs_data.jl b/test/fwds_rvs_data.jl
index 2536645f..c70d0bf0 100644
--- a/test/fwds_rvs_data.jl
+++ b/test/fwds_rvs_data.jl
@@ -24,13 +24,15 @@ end
     @testset "zero_rdata_from_type checks" begin
         @test Mooncake.can_produce_zero_rdata_from_type(Vector) == true
         @test Mooncake.zero_rdata_from_type(Vector) == NoRData()
-        @test Mooncake.can_produce_zero_rdata_from_type(FwdsRvsDataTestResources.Foo) == false
+        @test !Mooncake.can_produce_zero_rdata_from_type(FwdsRvsDataTestResources.Foo)
         @test Mooncake.can_produce_zero_rdata_from_type(Tuple{Float64, Type{Float64}})
         @test ==(
             Mooncake.zero_rdata_from_type(FwdsRvsDataTestResources.Foo),
             Mooncake.CannotProduceZeroRDataFromType(),
         )
         @test !Mooncake.can_produce_zero_rdata_from_type(Tuple)
+        @test !Mooncake.can_produce_zero_rdata_from_type(Union{Tuple{Float64}, Tuple{Int}})
+        @test !Mooncake.can_produce_zero_rdata_from_type(Tuple{T, T} where {T<:Integer})
     end
     @testset "lazy construction checks" begin
         # Check that lazy construction is in fact lazy for some cases where performance