Difference between async block and async fn

this basic tokio example, I got error
the trait bound fn() -> impl std::future::Future {hello}: std::future::Future is not satisfied: the trait std::future::Future is not implemented for fn() -> impl std::future::Future {hello}

however, rt.block_on(async { println!("Hello"); }); works. Why? what's the difference? Thanks.

use tokio::runtime::Runtime;
use tokio::prelude::*;

  fn main() {
    let mut rt = Runtime::new().unwrap();
   // This works
   // rt.block_on(async { println!("Hello"); });
  async fn hello() {

in Cargo.toml

tokio = { version = "0.2",  features = ["rt-core", "tcp", "macros", "dns", "io-util"] }

async fn is a function, so you should call it to get future.


Thanks, :+1:

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