Error returning eltype of SMatrix

[getzze]

Testing package GLVisualize.jl, I got an error in GLAbstarction.jl (https://github.com/JuliaGL/GLAbstraction.jl/blob/master/src/GLMatrixMath.jl). The error is:

LoadError: TypeError: UnionAll: expected Type, got Int64

It points to this function in GLMatrixMath.jl:

function (::Type{M})(q::Quaternions.Quaternion) where M <: Mat{3}
    T = eltype(M)
    sx, sy, sz = 2q.s*q.v1, 2q.s*q.v2,  2q.s*q.v3
    xx, xy, xz = 2q.v1^2,   2q.v1*q.v2, 2q.v1*q.v3
    yy, yz, zz = 2q.v2^2,   2q.v2*q.v3, 2q.v3^2
    T0, T1 = zero(T), one(T)
    Mat{3}(
        T1-(yy+zz), xy+sz,      xz-sy,
        xy-sz,      T1-(xx+zz), yz+sx,
        xz+sy,      yz-sx,      T1-(xx+yy)
    )
end

I figured out that checking the element type of some SMatrix gives me the same error:

eltype(Mat{3,3,Int, 9})  # Int64
eltype(Mat{3,3,Int})  # TypeError: UnionAll: expected Type, got Int64
eltype(Mat{3,Int})  # TypeError: UnionAll: expected Type, got Int64
eltype(Mat{Int})  # Any
eltype(Mat{3})  # TypeError: UnionAll: expected Type, got Int64

Is it related to the error in GLAbstarction.jl?

[tkoolen]

I can't reproduce with Julia 0.6.2 (or master) and StaticArrays master:

julia> using StaticArrays.FixedSizeArrays

julia> eltype(Mat{3,3,Int, 9})  # Int64
Int64

julia> eltype(Mat{3,3,Int})  # TypeError: UnionAll: expected Type, got Int64
Int64

julia> eltype(Mat{3,Int})  # TypeError: UnionAll: expected Type, got Int64
Any

julia> eltype(Mat{Int})  # Any
Any

julia> eltype(Mat{3})  # TypeError: UnionAll: expected Type, got Int64
Any

[getzze]

I'm using Julia 0.6.3 on ArchLinux. With a fresh start of julia (without loading any module), I get:

julia> using StaticArrays.FixedSizeArrays

julia> eltype(Mat{3,3,Int, 9})  # Int64
Int64

julia> eltype(Mat{3,3,Int})  # TypeError: UnionAll: expected Type, got Int64
Int64

julia> eltype(Mat{3,Int})  # TypeError: UnionAll: expected Type, got Int64
ERROR: TypeError: UnionAll: expected Type, got Int64

julia> eltype(Mat{Int})  # Any
ERROR: TypeError: UnionAll: expected Type, got Int64

julia> eltype(Mat{3})  # TypeError: UnionAll: expected Type, got Int64
Any

julia> eltype(Mat{3,3})
Any

I don't remember which modules were loaded last time, so I cannot reproduce. I still cannot load GLAbstraction.js though.

[tkoolen]

On 0.6.3 with StaticArrays master I can now reproduce the behavior in #423 (comment). Mat{3,Int} and Mat{Int} don't really make sense though (the first two type parameters should be integer values). The other ones produce the correct results, so I'm not sure if this is actionable.

I guess a better error message would be nice, but Julia currently has no way of expressing the constraint that a type parameter should be an integer value (e.g. 3), so in order to provide a better error message when methods are called on StaticArrays Types with 'nonsensical' type parameters, a check would need to be added to every such method.

By the way, the method in the issue description is technically type piracy. But in general, if you want to be able to write Mat{3}(q), you should probably define something like

function Mat{3}(q::Quaternions.Quaternion{T}) where {T}
    sx, sy, sz = 2q.s*q.v1, 2q.s*q.v2,  2q.s*q.v3
    xx, xy, xz = 2q.v1^2,   2q.v1*q.v2, 2q.v1*q.v3
    yy, yz, zz = 2q.v2^2,   2q.v2*q.v3, 2q.v3^2
    T0, T1 = zero(T), one(T)
    Mat{3}(
        T1-(yy+zz), xy+sz,      xz-sy,
        xy-sz,      T1-(xx+zz), yz+sx,
        xz+sy,      yz-sx,      T1-(xx+yy)
    )
end

Also note that Rotations.jl exists, is built on top of StaticArrays, and already has this functionality and a lot more.

[KristofferC]

Probably fixed by JuliaLang/julia#27404.

[getzze]

Ok, thanks a lot! I will report to the GLAbstraction.jl package maintainer.
Edit: JuliaGL/GLAbstraction.jl#91

[c42f]

This has long since been sorted out elsewhere I think.