Unexpectedly nice case of auto return type

[mipri]

On Friday, 6 December 2019 at 23:25:30 UTC, Johannes Loher wrote:
> On Tuesday, 3 December 2019 at 10:06:22 UTC, Mike Parker wrote:
>> On Tuesday, 3 December 2019 at 10:03:22 UTC, Basile B. wrote:
>>
>>>
>>> That's interesting details of D developement. Since you reply 
>>> to the first message I think you have not followed but in the 
>>> last reply I told that maybe we should be able to name the 
>>> type of null. I think this relates to TBottom too a bit.
>>
>> https://github.com/dlang/DIPs/blob/40352337053998885fbd0fe2718c300a322d3996/DIPs/DIP1NNN-DK.md
>
> This is everything I wished for. It basically exactly resembles 
> the results of the lengthy discussion H. S. Theo and I had in 
> the review thread for Walter‘s original bottom type suggestion. 
> And it even covers a few additional details we had not thought 
> about. I can’t wait for this DIP to go into review. Thanks a 
> lot to the DIP author. You have my biggest respect for writing 
> a fleshed out proposal of this!

nice.

Kotlin has this as well, with Unit as void and Nothing as
noreturn.

So for example this compiles without complaint:

   fun infinite(f: () -> Unit) {
       while (true) {
           f()
       }
   }

   fun main() {
       infinite { println(".") }
       println("goodbye")
   }

Where 'infinite' has an implcit Unit return type, but this
warns that the "goodbye" will never happen:

   fun infinite(f: () -> Unit): Nothing {
       while (true) {
           f()
       }
   }

   fun main() {
       infinite { println(".") }
       println("goodbye")
   }

This might be more important for resources that never get
closed, or secrets are never scrubbed from memory, due to
someone putting those tasks after a function like 'infinite'
without noticing.

... noreturn local variables are pretty gross, though.