error[E0308]: mismatched types --> $DIR/sugar.rs:12:7 | LL | a(x); | - ^ expected trait `Foo + Send`, found trait `Foo + Sync` | | | arguments to this function are incorrect | = note: expected struct `Box<(dyn Foo + Send + 'static)>` found struct `Box<(dyn Foo + Sync + 'static)>` note: function defined here --> $DIR/sugar.rs:5:4 | LL | fn a(_x: Box) { | ^ ----------------------- error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0308`.