`last(::Tuple{})` throws `BoundsError`

[nsajko]

`last(::Tuple{})` throws `BoundsError`

[KristofferC]

I think it is better to be consistent with other collections here.

[Seelengrab]

A MethodError would imply that the method doesn't exist - it does exist, but there's nothing to index since the collection is empty. A BoundsError is thus correct.

[nsajko]

A MethodError would imply that the method doesn't exist

The idea was that we could turn this into an actual "method not found" situation, something like:

function last(t::Tuple)
    function last_nonempty(t::Tuple{Any,Vararg})
        t[end]
    end
    last_nonempty(t)
end

julia> last((3,))
3

julia> last(())
ERROR: MethodError: no method matching (::var"#last_nonempty#1")(::Tuple{})
The function `last_nonempty` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  (::var"#last_nonempty#1")(::Tuple{Any, Vararg})

[nsajko]

Or, a bit more clear:

function last(t::Tuple)
    function throw_if_empty(t::Tuple{Any,Vararg})
        nothing
    end
    throw_if_empty(t)
    t[end]
end

[KristofferC]

The current way is most likely fine the way it is.