error[E0277]: `core::fmt::Opaque` cannot be shared between threads safely --> $DIR/send-sync.rs:8:10 | LL | send(format_args!("{:?}", c)); | ---- ^^^^^^^^^^^^^^^^^^^^^^^ `core::fmt::Opaque` cannot be shared between threads safely | | | required by a bound introduced by this call | = help: within `[core::fmt::ArgumentV1<'_>]`, the trait `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 `ArgumentV1<'_>` = note: required because it appears within the type `[ArgumentV1<'_>]` = note: required for `&[core::fmt::ArgumentV1<'_>]` to implement `Send` = note: required because it appears within the type `Arguments<'_>` note: required by a bound in `send` --> $DIR/send-sync.rs:1:12 | LL | fn send(_: T) {} | ^^^^ required by this bound in `send` error[E0277]: `core::fmt::Opaque` cannot be shared between threads safely --> $DIR/send-sync.rs:9:10 | LL | sync(format_args!("{:?}", c)); | ---- ^^^^^^^^^^^^^^^^^^^^^^^ `core::fmt::Opaque` cannot be shared between threads safely | | | required by a bound introduced by this call | = help: within `Arguments<'_>`, the trait `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 `ArgumentV1<'_>` = note: required because it appears within the type `[ArgumentV1<'_>]` = note: required because it appears within the type `&[ArgumentV1<'_>]` = note: required because it appears within the type `Arguments<'_>` note: required by a bound in `sync` --> $DIR/send-sync.rs:2:12 | LL | fn sync(_: T) {} | ^^^^ required by this bound in `sync` error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.