when will we have `@nogc nothrow` value exceptions in D?

[Paul Backus]

On Friday, 3 June 2022 at 23:13:39 UTC, Moth wrote:
> right now, trying to emulate exceptions in `@nogc nothrow` code 
> means i have to add 50 `if (errorCode != ErrorCode.Ok) { return 
> errorCode }`s everywhere, and use out parameters if i want to 
> actually return anything. it would be so much nicer [and 
> cleaner!] if there was some kind of language support for this.

Realistically: there's a good chance D never gets language 
support for this, and even if it does, it'll probably be a long 
time.

The best we can do in the short term is a Rust-style `Result` 
type with methods like [`andThen`][1], [`map`][2], and 
[`mapErr`][3] that allow us to chain functions together in a 
pipeline that automatically propagates errors.

[1]: 
https://doc.rust-lang.org/std/result/enum.Result.html#method.and_then
[2]: 
https://doc.rust-lang.org/std/result/enum.Result.html#method.map
[3]: 
https://doc.rust-lang.org/std/result/enum.Result.html#method.map_err