Nested views with static indexing (#657)

This allows StaticIndexing to appear at any position when making a view.

Author: mateuszbaran

src/indexing.jl

@@ -369,4 +369,13 @@ Base.checkindex(B::Type{Bool}, inds::AbstractUnitRange, i::StaticIndexing{T}) wh
 
 # unsafe_view
 
-Base.unsafe_view(A::AbstractArray, i::StaticIndexing{T}) where T = Base.unsafe_view(A, unwrap(i))
+# unsafe_view need only deal with vargs of `StaticIndexing`, as wrapped by to_indices.
+# i1 is explicitly specified to avoid ambiguities with Base
+Base.unsafe_view(A::AbstractArray, i1::StaticIndexing, indices::StaticIndexing...) = Base.unsafe_view(A, unwrap(i1), map(unwrap, indices)...)
+
+# Views of views need a new method for Base.SubArray because storing indices
+# wrapped in StaticIndexing in field indices of SubArray causes all sorts of problems.
+# Additionally, in some cases the SubArray constructor may be called directly
+# instead of unsafe_view so we need this method too (Base._maybe_reindex
+# is a good example)
+Base.SubArray(A::AbstractArray, indices::NTuple{<:Any,StaticIndexing}) = Base.SubArray(A, map(unwrap, indices))

test/indexing.jl

@@ -209,5 +209,18 @@ using StaticArrays, Test
         a = collect(11:20)
         @test view(a, SVector(1,2,3)) == [11,12,13]
         @test_throws BoundsError view(a, SVector(1,11,3))
+        B = rand(Int,3,4,5,6)
+        Bv = view(B, 1, (@SVector [2, 1]), [2, 3], (@SVector [4]))
+        @test Bv == B[1, [2,1], 2:3, [4]]
+        @test axes(Bv, 1) === SOneTo(2)
+        @test axes(Bv, 3) === SOneTo(1)
+        Bvv = view(Bv, (@SVector [1, 2]), 2, 1)
+        @test axes(Bvv) === (SOneTo(2),)
+        @test Bvv[1] == B[1, 2, 3, 4]
+        Bvv[1] = 100
+        @test Bvv[1] == 100
+        @test B[1,2,3,4] == 100
+        @test eltype(Bvv) == Int
+        @test Bvv[:] == [B[1,2,3,4], B[1,1,3,4]]
     end
 end