error: functions cannot be both `async` and C-variadic
  --> $DIR/not-async.rs:5:1
   |
LL | async unsafe extern "C" fn fn_cannot_be_async(x: isize, ...) {}
   | ^^^^^ `async` because of this                           ^^^ C-variadic because of this

error: functions cannot be both `async` and C-variadic
  --> $DIR/not-async.rs:12:5
   |
LL |     async unsafe extern "C" fn method_cannot_be_async(x: isize, ...) {}
   |     ^^^^^ `async` because of this                               ^^^ C-variadic because of this

error[E0700]: hidden type for `impl Future<Output = ()>` captures lifetime that does not appear in bounds
  --> $DIR/not-async.rs:5:62
   |
LL | async unsafe extern "C" fn fn_cannot_be_async(x: isize, ...) {}
   | ------------------------------------------------------------ ^^
   | |
   | opaque type defined here
   |
   = note: hidden type `{async fn body of fn_cannot_be_async()}` captures lifetime `'_`

error[E0700]: hidden type for `impl Future<Output = ()>` captures lifetime that does not appear in bounds
  --> $DIR/not-async.rs:12:70
   |
LL |     async unsafe extern "C" fn method_cannot_be_async(x: isize, ...) {}
   |     ---------------------------------------------------------------- ^^
   |     |
   |     opaque type defined here
   |
   = note: hidden type `{async fn body of S::method_cannot_be_async()}` captures lifetime `'_`

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0700`.