Nospecialize ::Channel functions that don't depend on {T}.

[NHDaly]

This is a follow up to #49508.

The expectation is that this should reduce compilation times (and possibly some dynamic dispatches, but probably not very often), with no penalty for the perf of the produced code, since we're only adding @nospecialize(::Channel) on the functions that don't reference data::Vector{T}.

• Mark most of the functions on Channels nospecialize when they don't depend on the data type in the Channel, T.
• Add precompile statement for Base.close(::Channel, ::Exception)

[NHDaly]

Are there good threading benchmarks we can run that will exercise Channels sufficiently well to ensure this is perf neutral after compilation and perf-positive if you include compilation?

[jakobnissen]

I think the @nospecialize f(x) = y syntax doesn't work - or am I wrong?

julia> @nospecialize f(x) = x + 1

julia> f(1)
ERROR: UndefVarError: `f` not defined

If I'm not mistaken, this is why the tests fail. You need to do f(@nospecialize(x::Channel)) = ....

[NHDaly]

Oh, thanks. Sad beans! It's interesting because you can of course do

@nospecialize
f(x) = y
@specialize

but i guess the one-function usage isn't supported. Thanks!