Improved StaticIndexing (issue #878) (#879)

* Improved StaticIndexing (issue #878)

* improve coverage

* fix test on 32-bit systems

* add subtyping

* fix

* disambiguation

* implement size

* don't `<:AbstractVector` for now

* remove disambiguation

Project.toml

@@ -1,6 +1,6 @@
 name = "StaticArrays"
 uuid = "90137ffa-7385-5640-81b9-e52037218182"
-version = "1.6.4"
+version = "1.6.5"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/indexing.jl

@@ -220,6 +220,40 @@ function Base.to_indices(A, I::Tuple{Vararg{Union{Integer, CartesianIndex, Stati
     return map(StaticIndexing, inds)
 end
 
+# Overloading getindex, size, iterate, lastindex and to_index is necessary to support
+# external operations that want to use to_indices on a StaticArray (see issue #878)
+
+function getindex(ind::StaticIndexing, i::Int)
+    return ind.ind[i]
+end
+
+function Base.size(ind::StaticIndexing)
+    return size(ind.ind)
+end
+
+function Base.length(ind::StaticIndexing)
+    return length(ind.ind)
+end
+
+function Base.iterate(ind::StaticIndexing)
+    return iterate(ind.ind)
+end
+function Base.iterate(ind::StaticIndexing, state)
+    return iterate(ind.ind, state)
+end
+
+function Base.firstindex(ind::StaticIndexing)
+    return firstindex(ind.ind)
+end
+
+function Base.lastindex(ind::StaticIndexing)
+    return lastindex(ind.ind)
+end
+
+function Base.to_index(ind::StaticIndexing)
+    return Base.to_index(ind.ind)
+end
+
 # getindex
 
 @propagate_inbounds function getindex(a::StaticArray, inds::Union{Int, StaticArray{<:Tuple, Int}, SOneTo, Colon}...)

test/indexing.jl

@@ -237,4 +237,20 @@ using StaticArrays, Test
         @test eltype(Bvv) == Int
         @test Bvv[:] == [B[1,2,3,4], B[1,1,3,4]]
     end
+
+    @testset "Supporting external code calling to_indices on StaticArray (issue #878)" begin
+        a = @SArray randn(2, 3, 4)
+        ind = to_indices(a, (CartesianIndex(1, 2), SA[2, 3]))
+        @test ind[1] === StaticArrays.StaticIndexing(1)
+        @test ind[3][2] === 3
+        @test (@inferred Base.to_index(ind[1])) === 1
+        @test (@inferred Base.to_index(ind[2])) === 2
+        @test (@inferred Base.to_index(ind[3])) === SA[2, 3]
+        @test (ind[3]...,) === (2, 3)
+        @test (@inferred length(ind[3])) === 2
+        @test length(ind) === 3
+        @test firstindex(ind[3]) === 1
+        @test lastindex(ind[3]) === 2
+        @test size(ind[3]) === (2,)
+    end
 end