use StaticArraysCore

[mcabbott]

Replaces StaticArrays with StaticArraysCore. Needed for JuliaDiff/ForwardDiff.jl#599

This means dropping Julia < 1.6.

There is a bit of a hack to get around the fact that Size isn't available. Looks like this is well-tested.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.84%. Comparing base (89f5a06) to head (f38c413).
Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #22      +/-   ##
==========================================
+ Coverage   86.48%   86.84%   +0.35%     
==========================================
  Files           1        1              
  Lines          74       76       +2     
==========================================
+ Hits           64       66       +2     
  Misses         10       10              

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[devmotion]

There is a bit of a hack to get around the fact that Size isn't available.

Maybe this should be fixed upstream and one should open issue in StaticArraysCore? It seems the docstring for similar_type (in StaticArraysCore) even mentions Size.

[mcabbott]

That would certainly minimise the diff here. But (1) that means a chain of 4 PRs to get ForwardDiff free, and (2) from a quick look it wasn't just a few lines to move Size. Maybe this package can be adjusted later, which is why I left the comments here.

In the meantime, are there any actual downsides to this approach? Simple tests seem so say vec compiles away.

[devmotion]

I opened an issue (JuliaArrays/StaticArraysCore.jl#12), so let's maybe see at least what the maintainers of StaticArraysCore think.

[devmotion]

Apparently the plan is to move Size to StaticArraysCore within the next few days, so I guess it would be good to wait with this PR until that's done.

[devmotion]

Size is now part of StaticArraysCore 1.4.0 🙂

[devmotion]

LGTM