Use struct in ParallelStencil

adapt_struct_ps.jl

using ParallelStencil
using ParallelStencil.FiniteDifferences2D
@init_parallel_stencil(CUDA, Float64, 2)

struct myStruct{T}
    val::T
end

n = 20
A = myStruct(@rand(n,n))
B = similar(A.val)

@parallel_indices (i, j) function bar!(B, A)
    B[i,j] = A.val[i,j]
    return nothing
end

import Adapt
function Adapt.adapt_structure(to, A::myStruct)
    val = Adapt.adapt_structure(to, A.val)
    myStruct(val)
end

@parallel (1:n, 1:n) bar!(B, A)

@assert all(Array(A.val) .== Array(B))