Alternatives to exceptions for error handling

[Vladimir Panteleev]

On Sunday, 22 November 2020 at 18:21:44 UTC, Paul Backus wrote:
> The biggest blocker for this is that D currently has no 
> equivalent of Rust's `#[must_use]` and C++'s `[[nodiscard]]`. I 
> have a DIP in the works to address this:
>
> https://github.com/dlang/DIPs/pull/193

This is great to see. Thank you for working on this.

Another approach that I'm not sure we've explored fully is to 
outright deprecate silently discarding all function return 
values. Functions which return a value that is only sometimes 
useful seem like a relatively rare oddity. I took a stab at 
implementing this as a DScanner check earlier this year:

https://github.com/dlang-community/D-Scanner/pull/819

Perhaps the most interesting product of the above is seeing what 
things were affected in Phobos. Most occurrences were in unit 
tests, which is understandable, and said breakages are probably 
more tolerable. Some valid patterns were affected though, such as 
returning `this` (as in the builder pattern). Perhaps it would 
make more sense to instead allow annotating functions as that 
it's safe to discard their return value (@discardable or such)?