Rebase @tspawnat to Base.@spawn for interpolation syntax

[wsphillips]

ThreadPools.jl/src/macros.jl

Lines 255 to 272 in 69a6b09

	macro tspawnat(thrdid, expr)
	thunk = esc(:(()->($expr)))
	var = esc(Base.sync_varname)
	tid = esc(thrdid)
	quote
	if $tid < 1 || $tid > Threads.nthreads()
	throw(AssertionError("@tspawnat thread assignment ($($tid)) must be between 1 and Threads.nthreads() (1:$(Threads.nthreads()))"))
	end
	local task = Task($thunk)
	task.sticky = false
	ccall(:jl_set_task_tid, Cvoid, (Any, Cint), task, $tid-1)
	if $(Expr(:isdefined, var))
	push!($var, task)
	end
	schedule(task)
	task
	end
	end

Could the interpolation syntax support present in Threads.@spawn be added here? Looks like it could be done fairly easily with a bit of copy-paste:

https://github.com/JuliaLang/julia/blob/02990278b31515a4212c2f5cbfe123661f2e26f2/base/threadingconstructs.jl#L166-L182

[tro3]

Interesting - I bet the Base.@spawn code got updated past v1.3, because at the time, the 1.3 code was mimicked as closely as possible. I'll check to see if an update here would break 1.3 compatibility, but otherwise this is a no-brainer.

[wsphillips]

It might, actually. I'm not sure if Base._lift_one_interp! was available in v1.3. I tested on v1.4.2. If it's indeed breaking for v1.3 could a reasonable workaround be to wrap the definitions in a conditional checking Julia's version? e.g. if Julia >1.4 use interpolated version, else existing? That ought to make the upgrade transparent and consistent with the functionality of @spawn by Julia version