error[E0277]: the size for values of type `str` cannot be known at compilation time --> $DIR/issue-38954.rs:1:10 | LL | fn _test(ref _p: str) {} | ^^^^^^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `str` = help: unsized fn params are gated as an unstable feature help: function arguments must have a statically known size, borrowed types always have a known size | LL | fn _test(ref _p: &str) {} | + error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.