error[E0277]: `core::fmt::Opaque` cannot be shared between threads safely
  --> $DIR/send-sync.rs:8:5
   |
LL | fn send<T: Send>(_: T) {}
   |            ---- required by this bound in `send`
...
LL |     send(format_args!("{:?}", c));
   |     ^^^^ `core::fmt::Opaque` cannot be shared between threads safely
   |
   = help: within `[std::fmt::ArgumentV1<'_>]`, the trait `std::marker::Sync` is not implemented for `core::fmt::Opaque`
   = note: required because it appears within the type `&core::fmt::Opaque`
   = note: required because it appears within the type `std::fmt::ArgumentV1<'_>`
   = note: required because it appears within the type `[std::fmt::ArgumentV1<'_>]`
   = note: required because of the requirements on the impl of `std::marker::Send` for `&[std::fmt::ArgumentV1<'_>]`
   = note: required because it appears within the type `std::fmt::Arguments<'_>`

error[E0277]: `core::fmt::Opaque` cannot be shared between threads safely
  --> $DIR/send-sync.rs:9:5
   |
LL | fn sync<T: Sync>(_: T) {}
   |            ---- required by this bound in `sync`
...
LL |     sync(format_args!("{:?}", c));
   |     ^^^^ `core::fmt::Opaque` cannot be shared between threads safely
   |
   = help: within `std::fmt::Arguments<'_>`, the trait `std::marker::Sync` is not implemented for `core::fmt::Opaque`
   = note: required because it appears within the type `&core::fmt::Opaque`
   = note: required because it appears within the type `std::fmt::ArgumentV1<'_>`
   = note: required because it appears within the type `[std::fmt::ArgumentV1<'_>]`
   = note: required because it appears within the type `&[std::fmt::ArgumentV1<'_>]`
   = note: required because it appears within the type `std::fmt::Arguments<'_>`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.