StaticIndexing breaks the to_indices interface

[rafaqz]

The to_indices docs state that:

The returned tuple must only contain either Ints or AbstractArrays of scalar indices that are supported by array A

But StaticIndexing is not either:

StaticArrays.jl/src/indexing.jl

Lines 213 to 221 in 217e6f1

	struct StaticIndexing{I}
	ind::I
	end
	unwrap(i::StaticIndexing) = i.ind
	function Base.to_indices(A, I::Tuple{Vararg{Union{Integer, CartesianIndex, StaticArray{<:Tuple,Int}}}})
	inds = to_indices(A, axes(A), I)
	return map(StaticIndexing, inds)
	end

See discourse:
https://discourse.julialang.org/t/a-sparse-matrix-cannot-be-indexed-by-a-svector/104265/5

[mbauman]

scalar indices that are supported by array A

This is exactly why the machinery passes A itself so deeply into the call stack here. Simple fix would be something like:

KnownStaticFriendlyArrays = Union{StaticArray, Array, #= others? ... =#}
static_index(A::KnownStaticFriendlyArray, ind) = StaticIndexing(ind)
static_index(A, ind) = ind
# ...
    return map(i->static_index(A, i), inds)

[mateuszbaran]

Probably duplicate of #878? See also #879.

[rafaqz]

@mbauman the docs still says AbstractArray of scalar indices even for known friendly types ;)

But absolutely, limiting it as to_indices(A::StaticArray, ... would fix the problem.