Could the definition of similar_type move here?

[ChrisRackauckas]

SciML/LabelledArrays.jl#122

It really should be in Base, but 🤷

[mateuszbaran]

Yes, that's reasonable.

[mateuszbaran]

I guess you also need the Size type and all similar_type methods it enables?

[ChrisRackauckas]

I don't, https://github.com/SciML/LabelledArrays.jl/pull/122/files#diff-918dda16160ab68d9766c22082a5c3463aef402c63fdf25244313c9f2bde525eR40

but I don't know if that's common. I worked around any Size issues like https://github.com/SciML/LabelledArrays.jl/pull/122/files#diff-918dda16160ab68d9766c22082a5c3463aef402c63fdf25244313c9f2bde525eR162

[mateuszbaran]

OK, so #5 is enough?

[devmotion]

This would be useful for ForwardDiff as well, it seems, as it uses similar_type in its implementations for StaticArrays.

Ref: JuliaDiff/ForwardDiff.jl#591

[N5N3]

I don't, https://github.com/SciML/LabelledArrays.jl/pull/122/files#diff-918dda16160ab68d9766c22082a5c3463aef402c63fdf25244313c9f2bde525eR40

but I don't know if that's common. I worked around any Size issues like https://github.com/SciML/LabelledArrays.jl/pull/122/files#diff-918dda16160ab68d9766c22082a5c3463aef402c63fdf25244313c9f2bde525eR162

@ChrisRackauckas looks like you still need the Size struct?

function StaticArrays.similar_type(::Type{SLArray{S, T, N, L, Syms}}, ::Type{NewElType},
                                   ::Size{NewSize}) where {S, T, N, L, Syms, NewElType, # used here
                                                           NewSize}

[ChrisRackauckas]

It can be worked around.

[N5N3]

Do you mean

function StaticArrays.similar_type(::Type{SLArray{S, T, N, L, Syms}}, ::Type{NewElType}, sz) where {S, T, N, L, Syms, NewElType}

?
This would cause ambiguity as we have

  similar_type(::Type{A}, ::Type{T}, s::Size{S}) where {A<:AbstractArray, T, S}