error[E0728]: `await` is only allowed inside `async` functions and blocks
  --> $DIR/issue-51751.rs:9:27
   |
LL | fn main() {
   |    ---- this is not `async`
LL |     let result = inc(10000);
LL |     let finished = result.await;
   |                           ^^^^^ only allowed inside `async` functions and blocks

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0728`.