I need to perform iteratively some operations slicewise in a multidimensional array, and I cannot make it type stable.

Here is an MWE in follow-up to the examples from eachslice is type unstable · Issue #39639 · JuliaLang/julia · GitHub

```
julia> arr = reshape(collect(1:27),3,3,3);
julia> function f3(arr, d)
for (i,x) in enumerate(eachslice(arr; dims=d))
@show sum(abs2,x)
end
end
f3 (generic function with 1 method)
julia> function f4(arr)
for (i,x) in enumerate(eachslice(arr; dims=(1,3)))
@show sum(abs2,x)
end
end
f4 (generic function with 1 method)
julia> @code_warntype f3(arr,(1,3))
MethodInstance for f3(::Array{Int64, 3}, ::Tuple{Int64, Int64})
from f3(arr, d) @ Main REPL[28]:1
Arguments
#self#::Core.Const(Main.f3)
arr::Array{Int64, 3}
d::Tuple{Int64, Int64}
Locals
@_4::Union{Nothing, Tuple{Tuple{Int64, SubArray{Int64, N, Array{Int64, 3}} where N}, Tuple{Int64, Tuple{CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, CartesianIndex{2}}}}}
value::Any
@_6::Int64
x::SubArray{Int64, N, Array{Int64, 3}} where N
i::Int64
Body::Nothing
...
julia> @code_warntype f4(arr)
MethodInstance for f4(::Array{Int64, 3})
from f4(arr) @ Main REPL[29]:1
Arguments
#self#::Core.Const(Main.f4)
arr::Array{Int64, 3}
Locals
@_3::Union{Nothing, Tuple{Tuple{Int64, SubArray{Int64, 1, Array{Int64, 3}, Tuple{Int64, Base.Slice{Base.OneTo{Int64}}, Int64}, true}}, Tuple{Int64, Tuple{CartesianIndices{2, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, CartesianIndex{2}}}}}
value::Int64
@_5::Int64
x::SubArray{Int64, 1, Array{Int64, 3}, Tuple{Int64, Base.Slice{Base.OneTo{Int64}}, Int64}, true}
i::Int64
...
```

As you can see, function f3 is type unstable, and function f4 is OK, and I cannot understand this.

How can I make f3 type-stable?