allow dims::Tuple in sum

Author: mcabbott

src/mapreduce.jl

@@ -158,6 +158,12 @@ end
     end
 end
 
+@inline function _mapreduce(f, op, D::Tuple, init, sz::Size{S}, a::StaticArray) where {S}
+    b = _mapreduce(f, op, first(D), init, sz, a)
+    return _mapreduce(f, op, Base.tail(D), init, Size(b), b)
+end
+_mapreduce(f, op, D::Tuple{}, init, sz::Size{S}, a::StaticArray) where {S} = a
+
 @generated function _mapfoldl(f, op, dims::Val{D}, init,
                                ::Size{S}, a::StaticArray) where {S,D}
     N = length(S)

test/mapreduce.jl

@@ -102,6 +102,7 @@ using Statistics: mean
         RSArray1 = SArray{Tuple{1,J,K}}  # reduced in dimension 1
         RSArray2 = SArray{Tuple{I,1,K}}  # reduced in dimension 2
         RSArray3 = SArray{Tuple{I,J,1}}  # reduced in dimension 3
+        RSArray13 = SArray{Tuple{1,J,1}}  # reduced in dimension 1 and 3
         a = randn(I,J,K); sa = OSArray(a)
         b = rand(Bool,I,J,K); sb = OSArray(b)
         z = zeros(I,J,K); sz = OSArray(z)
@@ -111,9 +112,11 @@ using Statistics: mean
         @test sum(sa) === sum(a)
         @test sum(abs2, sa) === sum(abs2, a)
         @test sum(sa, dims=2) === RSArray2(sum(a, dims=2))
+        @test sum(sa, dims=(2,)) === RSArray2(sum(a, dims=2))
         @test sum(sa, dims=Val(2)) === RSArray2(sum(a, dims=2))
         @test sum(abs2, sa; dims=2) === RSArray2(sum(abs2, a, dims=2))
         @test sum(abs2, sa; dims=Val(2)) === RSArray2(sum(abs2, a, dims=2))
+        @test_broken sum(abs2, sa; dims=(1,3)) === RSArray13(sum(abs2, a, dims=(1,3)))
 
         @test prod(sa) === prod(a)
         @test prod(abs2, sa) === prod(abs2, a)