Empty functions

[Jan Hönig]

I have asked this on StackOverflow[1]. I have received a valid 
answer, which solves my problem, however, I have still not 
understood, why some versions of it work and some don't.

The code is here[2].

I don't understand why `a` compiles just fine, while `b` and `c` 
don't.


I think, that I don't understand what `void function()` does or 
is.
Can someone explain it to me?


And I don't see why `(){}` works and `() => {}` does not.



[1]: 
https://stackoverflow.com/questions/64581514/void-lambda-function/64587101#64587101
[2]: https://run.dlang.io/is/GFe9Ht