support multiple return values? about tensorcast.jl HOT 4 OPEN

@cast rank1res[k] := rank1filter(permutedims(specs[k, :, :]))
@cast sproj[k, n, c] := rank1res[k][1][c, n]
@cast vs[k, c] := rank1res[k][2][c]
@cast λs[k] := rank1res[k][3]
@cast q[k] := rank1res[k][4]

@cast vi[j,k] := findmax(x[:, k])[j] 

x = randn(10, 20);
Base.ndims(::Tuple) = 1
@cast (v, i)[j][k] := findmax(x[:, k])[j] lazy
v

julia> x = rand(Int8, 3, 5)
3×5 Matrix{Int8}:
  76  -128   57   -8  -52
 -85    15  -33  -55  -20
  -2    -2  -29  -23  -17

julia> @cast vi[j,k] := findmax(x[:, k])[j] 
2×5 Matrix{Signed}:
 76  15  57  -8  -17
  1   2   1   1    3

julia> @cast (v, i)[j][k] := findmax(x[:, k])[j]
2-element Vector{SubArray{Signed, 1, LinearAlgebra.Transpose{Signed, Matrix{Signed}}, Tuple{Base.Slice{Base.OneTo{Int64}}, Int64}, false}}:
 [76, 15, 57, -8, -17]
 [1, 2, 1, 1, 3]

julia> v
5-element view(transpose(::Matrix{Signed}), :, 1) with eltype Signed:
  76
  15
  57
  -8
 -17

julia> @cast (v, i)[j][k] |= findmax(x[:, k])[j]  # less lazy
2-element Vector{Vector{Signed}}:
 [76, 15, 57, -8, -17]
 [1, 2, 1, 1, 3]

julia> @pretty @cast (v, i)[j][k] := findmax(x[:, k])[j]
begin
    ndims(x) == 2 || throw(ArgumentError("expected a 2-tensor x[:, k]"))
    local sandpiper = sliceview(x, (:, *))
    local butterfly = @__dot__(findmax(sandpiper))
    local raven = transmute(stack(butterfly), (2, 1))
    (v, i) = sliceview(raven, (:, *))
end

julia> x = rand(3, 5);

julia> @cast vi[j,k] := findmax(x[:, k])[j] 
2×5 Matrix{Real}:
 0.853762  0.394276  0.739257  0.347495  0.804691
 3         2         3         3         1

julia> @cast (v, i)[j][k] := findmax(x[:, k])[j];

julia> Int.(i)
5-element Vector{Int64}:
 3
 2
 3
 3
 1