[TensorAlgebra] [BUG] TensorAlgebra.blockedperm does not handle empty tuple correctly

[ogauthe]

using NDTensors.TensorAlgebra: TensorAlgebra
p1 = TensorAlgebra.blockedperm((),(2,1))
p2 = TensorAlgebra.blockedperm((),())
println(typeof(p1))
println(typeof(p2))

NDTensors.TensorAlgebra.BlockedPermutation{1, 2, Tuple{Tuple{Int64, Int64}}}
NDTensors.TensorAlgebra.BlockedPermutation{0, false, Tuple{}}

When both should be subtypes of NDTensors.TensorAlgebra.BlockedPermutation{2}

We previously discussed about removing this type and replacing it with a Tuple{Tuple} type. We need to decide whether to fix this or refactor the type.

[mtfishman]

Thanks for the report, should be easy to fix.

[mtfishman]

Seems like fixing this breaks some of the contract code since it is implicitly depending on this logic. I think some of the logic handling corner cases of fully contracted tensors is a bit misdesigned (related to #1428) so this will need to be fixed in conjunction with rewriting that logic.

[ogauthe]

fixed by #1459