Fix #18577, remove generated function broadcast_tup

[pabloferz]

No description provided.

[martinholters]

This seems to work:

@generated function broadcast_tup{AT,nargs,n}(f, As::AT, ::Type{Val{nargs}}, ::Type{Val{n}})
    Expr(:tuple, (Expr(:call, :f, (:(_broadcast_getindex(As[$i], $k)) for i=1:nargs)...) for k=1:n)...)
end

along with a changed call from broadcast_c to give the last parameter as a Val, too. I'm not claiming this is the best solution, but at least it seems to be a solution.

[martinholters]

IIUC, broadcast_c(f, ::Type{Tuple}, As...) is only called when all arguments As are Tuples or scalars. Then it might be worth to completely rewrite it to be inferable, but let's first try to fix the present issue ASAP in this PR.

[pabloferz]

@martinholters I updated with your version for now until we find a valid, inferrable and more efficient way of fixing this. By the way, at one moment I had Val{n} in #16986, but lost it somewhere between rebases.

[pabloferz]

@vtjnash Do you have a better suggestion for fixing this?

[vtjnash]

The non-generated version is also probably much more efficient:

function broadcast_tup(f, As, n)
    return (f((_broadcast_getindex(A, k) for A in As)...) for k = 1:n)...)
end

[pabloferz]

Removing the generated function seems the best option as this case wasn't inferable anyway (PR already updated accordingly).