vector indexing and `view` for `matrix` only accept `Int` indices instead of `Integer`

[matthias314]

view for Julia arrays accepts arbitrary integers and integer vectors. In AbstractAlgebra, only Int is allowed:

julia> a = ones(Int, 2, 3);

julia> view(matrix(a), :, Int8(1))
ERROR: MethodError: no method matching _view(::AbstractAlgebra.Generic.MatSpaceElem{Int64}, ::UnitRange{Int64}, ::Int8)
The function `_view` exists, but no method is defined for this combination of argument types.

julia> view(matrix(a), :, 1)
2-element AbstractAlgebra.Generic.MatSpaceVecView{Int64, Tuple{Base.Slice{Base.OneTo{Int64}}, Int64}, true}:
 1
 1

julia> view(a, :, Int8(1))
2-element view(::Matrix{Int64}, :, 1) with eltype Int64:
 1
 1

julia> view(matrix(a), :, Int8[1, 3])
ERROR: MethodError: no method matching _view(::AbstractAlgebra.Generic.MatSpaceElem{Int64}, ::UnitRange{Int64}, ::Vector{Int8})
The function `_view` exists, but no method is defined for this combination of argument types.

julia> view(matrix(a), :, [1, 3])
[1   1]
[1   1]

julia> view(a, :, Int8[1, 3])
2×2 view(::Matrix{Int64}, :, Int8[1, 3]) with eltype Int64:
 1  1
 1  1

The problem is the restriction to AbstractVector{Int} instead of AbstractVector{<:Integer} in the relevant methods:

AbstractAlgebra.jl/src/generic/Matrix.jl

Lines 62 to 76 in eb3aa9b

	function Base.view(M::Mat{T}, rows::Union{Colon, AbstractVector{Int}}, cols::Union{Colon, AbstractVector{Int}}) where T <: NCRingElement
	return MatSpaceView(view(M.entries, rows, cols), M.base_ring)
	end
	function Base.view(M::Mat{T}, rows::Int, cols::Union{Colon, AbstractVector{Int}}) where T <: NCRingElement
	return MatSpaceVecView(view(M.entries, rows, cols), M.base_ring)
	end
	function Base.view(M::Mat{T}, rows::Union{Colon, AbstractVector{Int}}, cols::Int) where T <: NCRingElement
	return MatSpaceVecView(view(M.entries, rows, cols), M.base_ring)
	end
	function Base.view(M::Mat{T}, rows::Int, cols::Int) where T <: NCRingElement
	return MatSpacePointView(view(M.entries, rows, cols), M.base_ring)
	end

EDIT: Ditto for vector indexing proper:

julia> matrix(a)[:, Int8(1)]
ERROR: MethodError: no method matching getindex(::AbstractAlgebra.Generic.MatSpaceElem{Int64}, ::UnitRange{Int64}, ::Int8)
The function `getindex` exists, but no method is defined for this combination of argument types.

julia> matrix(a)[:, Int8[1,3]]
ERROR: MethodError: no method matching sub(::AbstractAlgebra.Generic.MatSpaceElem{Int64}, ::UnitRange{Int64}, ::Vector{Int8})
The function `sub` exists, but no method is defined for this combination of argument types.