Lemmy Server's (lemmy_server) Rust code, stuck on use of return and how the general Ok / error return works (lemmy.ml)

submitted 3 years ago* (last edited 3 years ago) by RoundSparrow@lemmy.ml to c/rust@lemmy.ml

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I haven't had this much trouble since Ada coding in 1986 when I was age 16.

Can someone please help me get the procedural syntax right?

https://github.com/LemmyNet/lemmy/pull/3805

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[-] TehPers@beehaw.org 2 points 3 years ago* (last edited 3 years ago)

Also worth mentioning, but you can early-return from a block in rust too, just using the break keyword and named blocks:

let x = 'my_block {
    if thing() { break 'my_block 1; }
    2
};

Edit: I haven't tried this with async blocks, but I'm guessing it works there too?

[-] nous@programming.dev 3 points 3 years ago

Flow control like return and break work differently in async blocks. They are much closer to closures than blocks in this regard. And need to be as they are lazily evaluated (like closures) and may even be evaluated well after the code that contains them has finished.

[-] TehPers@beehaw.org 1 points 3 years ago

Looks like labels don't work on async blocks, but using a nested inner block does work. Also, yeah, async blocks only exist to create Futures, they don't execute until you start polling them. I don't really see any reason why you couldn't stick a label on the async block itself though, breaking would at worst just create one new state for the future - early returned.

this post was submitted on 03 Aug 2023

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