Async: Constrain lifetime of Fut type param to lifetime of for<'func>F: Fn(..) -> Fut

vague · March 11, 2023, 5:44am

Box::pin is the easiest way to do it. Otherwise, it won't be ergonomic. Also see How to express that the Future returned by a closure lives only as long as its argument?

BTW, I've added the code here as an example of showing how it can be acheived with my crate async_closure:

github.com

zjp-CN/async_closure/blob/e43879d579ce969e75fed6c9b003cc601e8ca670/examples/urlo.rs#L83-L92


      
          async fn generic_fn<'env, T, F>(f: F) -> Result<()>
          where
              F: AsyncFnOnce<'env, (), Output = Result<T>>,
              T: std::fmt::Display,
          {
              let t = f.call_once(()).await?;
              println!("{t}");
          
              Ok(())
          }

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Async: Constrain lifetime of Fut type param to lifetime of for<'func>F: Fn(..) -> Fut

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