LL | async fn frob(self) {}
| ^^^^ doesn't have a size known at compile-time
|
- = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `str`
+ = help: within `Foo`, the trait `Sized` is not implemented for `str`
= note: required because it appears within the type `Foo`
= help: unsized locals are gated as an unstable feature
help: function arguments must have a statically known size, borrowed types always have a known size