error[E0277]: the size for values of type `T` cannot be known at compilation time --> $DIR/unsized-fn-arg.rs:5:17 | LL | fn f(t: T) {} | - ^ doesn't have a size known at compile-time | | | this type parameter needs to be `Sized` | = help: unsized fn params are gated as an unstable feature help: consider removing the `?Sized` bound to make the type parameter `Sized` | LL - fn f(t: T) {} LL + fn f(t: T) {} | help: function arguments must have a statically known size, borrowed types always have a known size | LL | fn f(t: &T) {} | + error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.