Strange performance issue on 1.9.0-rc3

[MilesCranmer]

Okay I think I might have figured out the issue thanks to Cthulhu:

I did not realize this, but apparently Julia does not perform multiple dispatch on keyword arguments? Is that (still) true?

Force specialization on kwargs

If I have a function like this: f_vararg(varargs::Int...) = tuple(varargs...) I can force specialization on varargs with either of the following: g_vararg(varargs::Vararg{Int, N}) where {N} = tuple(varargs...) h_vararg(varargs::Vararg{<:Any, N}) where {N} = tuple(varargs...) Now suppose instead that I have a function like this: f_kwarg(; kwargs...) = (; kwargs...) How can I force specialization on the keyword arguments?

If so then I suppose I need to specify this result_type as a normal argument, rather than a kwarg. Otherwise it thinks the return type is Any, because result_type could be anything.