[steveklabnik]

It is a great strategy. One of my favorite examples of this is Rust. When talking about what synatax "await" should use, we decided on a postfix syntax: "foo.await" . But there was concern that because JavaScript and other languages use "await foo", it would be confusing.

Solution?

  async fn foo() {
      
  }
  
  fn main() {
      let x = async { await foo() };
  }

  error: incorrect use of `await`
   --> src/main.rs:6:13
    |
  6 |       let x = async { await foo() };
    |                       ^^^^^^^^^^^ help: `await` is a postfix operation: `foo().await`

Do exactly that: parse the incorrect form and emit a good diagnostic.