Minimal changes to enable import on v0.6

[rdeits]

This is not ready for merge yet, but I just wanted to get a sense of what would be required to even import GeometryTypes in Julia v0.6-dev.

The tests don't all pass, because there seem to be issues with FixedSizeArrays fsa_abstract() like:

type UnionAll has no field name
  Stacktrace:
   [1] fsa_abstract(...) at /Users/rdeits/.julia/v0.6/FixedSizeArrays/src/core.jl:44
   [2] ndims(...) at /Users/rdeits/.julia/v0.6/FixedSizeArrays/src/core.jl:30
   [3] Type(...) at /Users/rdeits/.julia/v0.6/FixedSizeArrays/src/constructors.jl:64
   [4] macro expansion at /Users/rdeits/.julia/v0.6/GeometryTypes/test/gjk.jl:9 [inlined]

but this at least fixes failures on import.

The primary change is that in Julia v0.6, if you have an abstract type:

abstract Foo{T}

then you can't subtype from Foo (without the parameter). So this is an error:

abstract Bar <: Foo

but this is still OK:

abstract Bar{T} <: Foo{T}

See: JuliaLang/julia#19414

The fix was to explicitly include the N and T parameters in the various Mesh types so that we can have abstract AbstractMesh{N, T, VertT, FaceT} <: AbstractGeometry{N, T} instead of abstract AbstractMesh{VertT, FaceT} <: AbstractGeometry

Now that we have triangular dispatch in v0.6, it might be possible to do this in a more clever way. I'm not sure yet.

[rdeits]

Is moving to StaticArrays still in the cards? That might be the best way to improve v0.6 compatibility.

[SimonDanisch]

Yes moving to StaticArrays is the way forward!

[rdeits]

Is that something you'd like help with?

[SimonDanisch]

Thanks Robin! Yes if you want to get into this, you could start here:
#76
Didn't notice, that it wasn't actually a pull request up to now.
You can try out if that branch works for you and then we can go from there ;)
Although I believe, the main problem is getting this back to work on 0.6:
https://github.com/JuliaArrays/StaticArrays.jl/blob/master/src/StaticArrays.jl#L54

[rdeits]

Great! I'll take a look over at #76.

[rdeits]

@SimonDanisch I think the PR at #76 has the wrong commits attached. It doesn't look like it has any of the StaticArrays changes.

Anyway, I've started looking into this. It'll be a while before I really understand what needs to be done, but I've at least managed to uncover something weird that will have to be resolved to fix v0.6 compatibility: JuliaArrays/StaticArrays.jl#106

[SimonDanisch]

Oh yeah, true! but from what I remember, I tried to keep the changes in GeometryTypes itself minimal.
And the biggest change (changing the face type) is already merged, if I remember correctly...