fix recursivecopy as discussed in SciML/OrdinaryDiffEq.jl#1386

Closes SciML/OrdinaryDiffEq.jl#1386

Author: ranocha

Project.toml

@@ -27,9 +27,10 @@ ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 NLsolve = "2774e3e8-f4cf-5e23-947b-6d7e65073b56"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
+StructArrays = "09ab397b-f2b6-538f-b94a-2f83cf4a842a"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["ForwardDiff", "NLsolve", "OrdinaryDiffEq", "Test", "Unitful", "Random", "Zygote"]
+test = ["ForwardDiff", "NLsolve", "OrdinaryDiffEq", "Test", "Unitful", "Random", "StructArrays", "Zygote"]

src/utils.jl

@@ -7,7 +7,12 @@ function recursivecopy(a::AbstractArray{T,N}) where {T<:Number,N}
 end
 
 function recursivecopy(a::AbstractArray{T,N}) where {T<:AbstractArray,N}
-  map(recursivecopy,a)
+  if ArrayInterface.ismutable(a)
+    b = similar(a)
+    map!(recursivecopy, b, a)
+  else
+    ArrayInterface.restructure(a, map(recursivecopy, a))
+  end
 end
 
 function recursivecopy!(b::AbstractArray{T,N},a::AbstractArray{T2,N}) where {T<:StaticArray,T2<:StaticArray,N}

test/copy_static_array_test.jl

@@ -1,4 +1,4 @@
-using Test, RecursiveArrayTools, StaticArrays
+using Test, RecursiveArrayTools, StaticArrays, StructArrays
 
 struct ImmutableFV <: FieldVector{2,Float64}
     a::Float64
@@ -64,3 +64,19 @@ a[2][1] *= 5
 b[1] = 2*b[1]
 copyat_or_push!(a, 2, b[1])
 @test a[2] == b[1]
+
+# StructArray of Immutable FieldVector
+a = StructArray([ImmutableFV(1., 2.)])
+b = recursivecopy(a)
+@test typeof(a) == typeof(b)
+@test a[1] == b[1]
+a[1] *= 2
+@test a[1] != b[1]
+
+# StructArray of Mutable FieldVector
+a = StructArray([MutableFV(1., 2.)])
+b = recursivecopy(a)
+@test typeof(a) == typeof(b)
+@test a[1] == b[1]
+a[1] *= 2
+@test a[1] != b[1]