The following code:
const ulong[] A = [1UL];
const ulong[] B = A ~ [1UL];
gives:
concat.d(2): Error: non-constant expression A ~ [1LU]
But changing it to the following works:
const ulong[] A = [1UL];
const ulong[] B = getConcat(A, [1UL]);
ulong[] getConcat(ulong[] a, ulong[] b)
{
return a ~ b;
}