4 ms·

Super excited to see async/await finally get close to MVP and landing. I am not a huge fan of ".await", but there isn't much more to be said -- my personal pref

by cyphar 8y ago

Super excited to see async/await finally get close to MVP and landing. I am not a huge fan of ".await", but there isn't much more to be said -- my personal preference of "#await" or "@await" does look like line-noise and I think there's no perfect answer to this one (await{} was too messy and no better than prefix-await, and (await foo))? had too many brackets). I also appreciate that this proposal was insanely bike-shedded and so really, any decision is better than no decision. I would've been happy with "await << f()" if it meant we could get this feature (lots of Rust projects I'm interested in are waiting on async/await before focusing on further development).

blattimwind 8y ago
Wouldn't "await expr" or "await@expr" (if you hate whitespace) make more sense compared to "expr await"? let db_conn = await pool.connect() (Which is what e.g. Python uses, with the downside that you tend to need to parenthize more because await has very low precedence). vs let db_conn = pool.connect() await .await is not soo bad, kinda method-y let db_conn = pool.connect().await
- eslaught 8y ago
  Did you see the previous post on this topic? They discussed this extensively: https://paper.dropbox.com/doc/Await-Syntax-Write-Up--AcIbhZ1tPTCloXb2fmFpBTt~Ag-t9NlOSeI4RQ8AINsaSSyJ https://paper.dropbox.com/doc/Await-Syntax-Write-Up--AcIbhZ1...
- cyphar 8y ago
  I don't think "expr await" would be a good choice but that isn't the decision that was made, and I wasn't arguing for it in the first place. TFA says that using alternative punctuation was decided against because it would lead to line-noise and I don't think there's much more to discuss -- I understand that position and respect it. My main issue with .await is that it does look method-y rather than keyword-y. But while I like Python's "await expr" syntax in Python the existence of ? and chaining of methods in Rust justifies having a different syntax for it.
  - int_19h 8y ago
    Python also chains methods. And having to write (await (await (await foo).bar()).baz()) is annoying.
    - imtringued 8y ago
      That doesn't look like well written async code at all... You're not supposed to use await literally everywhere and especially not multiple times in a single line. Javascript already has an answer to this (Hint it was inspired by Monads but it isn't one): await foo.then(f => f.bar()).then(b => b.baz())
      - int_19h 8y ago
        What happens if f.bar() throws an exception asynchronously?
McWobbleston 8y ago
@await does look like line noise, but if they're considering giving other constructs a postfix syntax, I think the noise is justified. Overloading the dot operator creates confusion, it gives the impression that .await is somehow related to data access instead of control flow

by cyphar 8y ago

blattimwind 8y ago

Wouldn't "await expr" or "await@expr" (if you hate whitespace) make more sense compared to "expr await"? let db_conn = await pool.connect() (Which is what e.g. Python uses, with the downside that you tend to need to parenthize more because await has very low precedence). vs let db_conn = pool.connect() await .await is not soo bad, kinda method-y let db_conn = pool.connect().await

eslaught 8y ago
Did you see the previous post on this topic? They discussed this extensively: https://paper.dropbox.com/doc/Await-Syntax-Write-Up--AcIbhZ1tPTCloXb2fmFpBTt~Ag-t9NlOSeI4RQ8AINsaSSyJ https://paper.dropbox.com/doc/Await-Syntax-Write-Up--AcIbhZ1...
cyphar 8y ago
I don't think "expr await" would be a good choice but that isn't the decision that was made, and I wasn't arguing for it in the first place. TFA says that using alternative punctuation was decided against because it would lead to line-noise and I don't think there's much more to discuss -- I understand that position and respect it. My main issue with .await is that it does look method-y rather than keyword-y. But while I like Python's "await expr" syntax in Python the existence of ? and chaining of methods in Rust justifies having a different syntax for it.
- int_19h 8y ago
  Python also chains methods. And having to write (await (await (await foo).bar()).baz()) is annoying.
  - imtringued 8y ago
    That doesn't look like well written async code at all... You're not supposed to use await literally everywhere and especially not multiple times in a single line. Javascript already has an answer to this (Hint it was inspired by Monads but it isn't one): await foo.then(f => f.bar()).then(b => b.baz())
    - int_19h 8y ago
      What happens if f.bar() throws an exception asynchronously?

McWobbleston 8y ago

@await does look like line noise, but if they're considering giving other constructs a postfix syntax, I think the noise is justified. Overloading the dot operator creates confusion, it gives the impression that .await is somehow related to data access instead of control flow