A final proposal for await syntax

[scottmcm]

@josh

I made a particular function too slow because three things that were supposed to happen in parallel happened one after the other, again because I just took the convenient route of .await without thinking about it.

What would code that awaits multiple futures in parallel (rather than in series) typically look like?

In C#, I yesterday (literally -- I just checked) gave the "you should do that in parallel" feedback for this code (domain object names obfuscated, but the code is otherwise untouched):

var sprockets = await this.ExtractContent<SprocketContent>(SprocketPath);
var widgets = await this.ExtractContent<WidgetContent>(WidgetPath);
var spanners = await this.ExtractContent<SpannerContent>(SpannerPath);

So I think prefix await isn't immune to "just await without thinking about it" either.

That said, it's a pain in C# to do this differently, because Task.WhenAll only supports the homogeneous case. If I understand How will Promise.all be implemented? - #4 by Matthias247 correctly, then this will be way better in Rust -- whether prefix or postfix -- as it could be

let (sprockets, widgets, spanners) = join!(
    self.extract_content::<SprocketContent>(SPROCKET_PATH),
    self.extract_content::<WidgetContent>(WIDGET_PATH),
    self.extract_content::<SpannerContent>(SPANNER_PATH),
).await;

@josh

That looks like syntax highlighting that hasn’t been updated to know about the await (or async) keyword. await should use the same color as let and fn and use do.

+1, and I wonder if that actually makes .await less noticeable than with no highlighting, as one's brain starts relying on the colours for mental parsing shortcuts.