fix 1d mapslices (#661)

Author: rafaqz

src/array/methods.jl

@@ -109,7 +109,7 @@ end
     ds = DD.dims(A, _astuple(dims))
     # Run one slice with dimensions to get the transformed dim
     d_inds = map(d -> rebuild(d, 1), otherdims(A, ds))
-    example_dims = DD.dims(f(view(A, d_inds...)))
+    example_dims = length(d_inds) > 0 ? DD.dims(f(view(A, d_inds...))) : ()
     replacement_dims = if isnothing(example_dims) || length(example_dims) != length(ds)
         map(d -> rebuild(d, NoLookup()), ds)
     else

test/methods.jl

@@ -366,6 +366,12 @@ end
         @test size(y) == size(dims(y))
         @test dims(y) == dims(x[2:9, :, :])
     end
+
+    @testset "single dim" begin
+        x = X(1:10)
+        A = DimArray(ones(10), x)
+        @test mapslices(sum, A; dims=X) == fill(10.0, X(1))
+    end
 end
 
 @testset "cumsum" begin