DIP 1017--Add Bottom Type--Community Review Round 1

[Stefan Koch]

On Thursday, 9 August 2018 at 03:02:55 UTC, Mike Parker wrote:
> This is the feedback thread for the first round of Community 
> Review for DIP 1017, "Add Bottom Type":
>
> [ ... ]

Regarding the rationale:

It should be pointed out that this is a further complication of 
the type-system (which is already more complex than what c++ has).
That does impact generic code.

My own experience with generic code has show that it is very hard 
(practically impossible) to write correct code,
(correct meaning here working as intended, when instantiation 
succeeds) even when using template constraints.

There is no explanation of when the additional optimizations 
would be actually relevant,
Usually functions that don't return abort the program anyway.

There not even an example piece of code where the newly enabled 
optimizations would make an impact.

The point about other system languages having this feature is 
actually the most substantiated one :)

I could accept a rationale which is about being able to simplify 
and extend the applicability of  CFA (control flow analysis).
Though even than CFA, not really that effective when is comes to 
making faster code.
It is however quite good at subtly breaking code :(

TLDR;

I would kindly recommend further expansion on the interactions 
with the rest of the language and implications thereof..

Regards,

Stefan