Add eachindex method for OptionallyStaticRanges and fix an error when using StaticArrays <v1.

Author: chriselrod

src/ArrayInterface.jl

@@ -760,7 +760,11 @@ function __init__()
         end
         t
     end
-    parent_type(::Type{<:StaticArrays.SizedArray{S, T, M, N, A}}) where {S,T,M,N,A} = A
+    if StaticArrays.SizedArray{Tuple{8, 8}, Float64, 2, 2} isa UnionAll
+        parent_type(::Type{<:StaticArrays.SizedArray{S, T, M, N, A}}) where {S,T,M,N,A} = A
+    else
+        parent_type(::Type{<:StaticArrays.SizedArray{S, T, M, N}}) where {S,T,M,N} = Array{T,N}
+    end
     @require Adapt="79e6a3ab-5dfb-504d-930d-738a2a938a0e" begin
       function Adapt.adapt_storage(::Type{<:StaticArrays.SArray{S}},xs::Array) where S
           StaticArrays.SArray{S}(xs)

src/ranges.jl

@@ -372,6 +372,8 @@ end
 
 const OptionallyStaticRange = Union{<:OptionallyStaticUnitRange,<:OptionallyStaticStepRange}
 
+Base.eachindex(r::OptionallyStaticRange) = r
+
 Base.to_shape(x::OptionallyStaticRange) = length(x)
 Base.to_shape(x::Slice{T}) where {T<:OptionallyStaticRange} = length(x)