Instantiate per-partition Broadcasted in NamedArrayPartition copyto!

src/named_array_partition.jl

@@ -220,7 +220,7 @@ end
     )
     N = npartitions(dest, bc)
     @inbounds for i in 1:N
-        copyto!(getfield(dest, :array_partition).x[i], unpack(bc, i))
+        copyto!(getfield(dest, :array_partition).x[i], Broadcast.instantiate(unpack(bc, i)))
     end
     return dest
 end

test/Core/named_array_partition_tests.jl

@@ -81,3 +81,31 @@ end
     x[1] = 99.0
     @test x[1] == 99.0
 end
+
+@testset "NamedArrayPartition broadcast instantiates partition Broadcasted" begin
+    # Mirrors the same fix in ArrayPartition broadcast: copyto! unpacks each partition's
+    # slice of the Broadcasted tree without recomputing its axes (unpack drops them), so
+    # the partition's own copyto! must get an instantiated Broadcasted (axes !== nothing).
+    mutable struct RATRecordingArray2{T} <: AbstractVector{T}
+        data::Vector{T}
+        instantiated::Bool
+    end
+    RATRecordingArray2(v::Vector) = RATRecordingArray2(v, false)
+    Base.size(a::RATRecordingArray2) = size(a.data)
+    Base.getindex(a::RATRecordingArray2, i::Int) = a.data[i]
+    Base.setindex!(a::RATRecordingArray2, v, i::Int) = (a.data[i] = v)
+    function Base.similar(a::RATRecordingArray2, ::Type{T}, dims::Dims) where {T}
+        return RATRecordingArray2(similar(a.data, T, dims), false)
+    end
+    Base.BroadcastStyle(::Type{<:RATRecordingArray2}) = Broadcast.ArrayStyle{RATRecordingArray2}()
+    function Base.copyto!(dest::RATRecordingArray2, bc::Broadcast.Broadcasted{<:Broadcast.ArrayStyle{RATRecordingArray2}})
+        dest.instantiated = bc.axes !== nothing
+        copyto!(dest.data, Broadcast.instantiate(bc))
+        return dest
+    end
+
+    nap = NamedArrayPartition(a = RATRecordingArray2([1.0, 2.0]), b = RATRecordingArray2([1.0, 2.0, 3.0]))
+    nap2 = NamedArrayPartition(a = RATRecordingArray2([1.0, 1.0]), b = RATRecordingArray2([1.0, 1.0, 1.0]))
+    nap .= nap .+ nap2
+    @test all(x -> x.instantiated, ArrayPartition(nap).x)
+end

test/QA/qa.jl

@@ -20,7 +20,7 @@ run_qa(
                 :QRCompactWY, :SolvedVariables, :StaticArray, :StaticVecOrMat,
                 :SymbolicTypeTrait, :_InitialValue, :_ipiv_rows!, :_maybe_reshape,
                 :_swap_rows!, :_unsafe_getindex, :_unsafe_getindex!, :adapt_structure,
-                :add_sum, :flatten, :front, :index_shape, :ismutable, :issingular,
+                :add_sum, :flatten, :front, :index_shape, :instantiate, :ismutable, :issingular,
                 :promote_op, :restructure, :result_style, :similar_type, :tail,
                 :unalias, :zeromatrix,
             ),