Note the parentheses in the last suggestion:
```
error[E0277]: the size for values of type `(dyn Foo + Send + 'static)` cannot be known at compilation time
--> $DIR/not-on-bare-trait.rs:7:8
|
LL | fn foo(_x: Foo + Send) {
| ^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `(dyn Foo + Send + 'static)`
= help: unsized fn params are gated as an unstable feature
help: you can use `impl Trait` as the argument type
|
LL | fn foo(_x: impl Foo + Send) {
| ++++
help: function arguments must have a statically known size, borrowed types always have a known size
|
LL | fn foo(_x: &(Foo + Send)) {
| ++ +
```
