why cannot spawn function defined in unittest block {}?

[mw]

On Saturday, 20 June 2020 at 18:01:51 UTC, Adam D. Ruppe wrote:
> On Saturday, 20 June 2020 at 17:43:42 UTC, mw wrote:
>> the function defined in unittest become a delegate? how to 
>> work-around this?
>
> just add the keyword static to the functions

https://github.com/mingwugmail/dlang_tour/blob/master/spawn_in_unittest.d#L50

Tried, still doesn't work:

$ dmd -unittest spawn_in_unittest.d
spawn_in_unittest.d(57): Error: static function 
spawn_in_unittest.__unittest_L33_C1.threadProducer cannot access 
frame of function spawn_in_unittest.__unittest_L33_C1
spawn_in_unittest.d(74): Error: static function 
spawn_in_unittest.__unittest_L33_C1.threadConsumer cannot access 
frame of function spawn_in_unittest.__unittest_L33_C1