error[E0277]: `T` cannot be sent between threads safely --> $DIR/builtin-superkinds-double-superkind.rs:6:32 | LL | impl Foo for (T,) { } | ^^^^ `T` cannot be sent between threads safely | = note: required because it appears within the type `(T,)` note: required by a bound in `Foo` --> $DIR/builtin-superkinds-double-superkind.rs:4:13 | LL | trait Foo : Send+Sync { } | ^^^^ required by this bound in `Foo` help: consider further restricting this bound | LL | impl Foo for (T,) { } | +++++++++++++++++++ error[E0277]: `T` cannot be shared between threads safely --> $DIR/builtin-superkinds-double-superkind.rs:9:24 | LL | impl Foo for (T,T) { } | ^^^^^ `T` cannot be shared between threads safely | = note: required because it appears within the type `(T, T)` note: required by a bound in `Foo` --> $DIR/builtin-superkinds-double-superkind.rs:4:18 | LL | trait Foo : Send+Sync { } | ^^^^ required by this bound in `Foo` help: consider further restricting this bound | LL | impl Foo for (T,T) { } | +++++++++++++++++++ error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.