Better handling of subtypes of StaticVector in views of SizedArray (#867)

* Better handling of subtypes of StaticVector in views of SizedArray

* Update src/SizedArray.jl

Co-authored-by: Chris Foster <chris42f@gmail.com>

Co-authored-by: Chris Foster <chris42f@gmail.com>

Author: mateuszbaran

src/SizedArray.jl

@@ -200,13 +200,16 @@ end
 
 ### Code that makes views of statically sized arrays also statically sized (where possible)
 
+# Note, _get_static_vector_length is used in a generated function so it's strictly internal and can't be extended
+_get_static_vector_length(::Type{<:StaticVector{N}}) where {N} = N
+
 @generated function new_out_size(::Type{Size}, inds...) where Size
     os = []
     map(Size.parameters, inds) do s, i
         if i <: Integer
             # dimension is fixed
         elseif i <: StaticVector
-            push!(os, i.parameters[1].parameters[1])
+            push!(os, _get_static_vector_length(i))
         elseif i == Colon || i <: Base.Slice
             push!(os, s)
         elseif i <: SOneTo

test/SizedArray.jl

@@ -206,6 +206,10 @@
         x5 = view(x, :)
         @test isa(x5, SizedArray{Tuple{24},Float64,1,1,<:SubArray{Float64,1}})
         @test x5 == view(x.data, :)
+
+        x6 = view(x, StaticArrays.SUnitRange(2, 3), :, 2)
+        @test isa(x6, SizedArray{Tuple{2,3},Float64,2,2,<:SubArray{Float64,2}})
+        @test x6 == view(x.data, StaticArrays.SUnitRange(2, 3), :, 2)
     end
 
     @testset "views of MArray" begin