error[E0277]: the trait bound `&Box i32>: Foo` is not satisfied --> $DIR/call-on-unimplemented-with-autoderef.rs:8:15 | LL | needs_foo(x); | --------- ^ the trait `Foo` is not implemented for `&Box i32>` | | | required by a bound introduced by this call | note: required by a bound in `needs_foo` --> $DIR/call-on-unimplemented-with-autoderef.rs:5:22 | LL | fn needs_foo(_: impl Foo) {} | ^^^ required by this bound in `needs_foo` help: use parentheses to call this trait object | LL | needs_foo(x()); | ++ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.