Ask questionsE0373 help suggests `move async` but the correct syntax is `async move`

E0373 help suggests appending move in front of async closures:

error[E0373]: closure may outlive the current function, but it borrows `n`, which is owned by the current function
  --> src/
10 |         Box::pin((async || {
   |                   ^^^^^^^^ may outlive borrowed value `n`
11 |             Some((n, n + 1))
   |                   - `n` is borrowed here
note: closure is returned here
  --> src/
10 | /         Box::pin((async || {
11 | |             Some((n, n + 1))
12 | |         })())
   | |_____________^
help: to force the closure to take ownership of `n` (and any other referenced variables), use the `move` keyword
10 |         Box::pin((move async || {
   |                   ^^^^^^^^^^^^^

but move async is not in the correct order:

error: expected one of `|` or `||`, found `async`
  --> src/
10 |         Box::pin((move async || {
   |                        ^^^^^ expected one of `|` or `||` here

The suggestion should be async move || { ... instead.

Meta: rustc 1.37.0-nightly (4edff843d 2019-06-16)


Answer questions estebank

Marking as "deferred" because async closures are not a candidate for stabilization

@cramertj if we're making the suggestion now then it is wrong and we should at least hide it. Users will get confused if they are offered a feature that is not yet stable, and even worse offered it with the wrong syntax.

cc @rust-lang/wg-diagnostics


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