error[E0277]: the size for values of type `(dyn Foo + 'static)` cannot be known at compilation time --> $DIR/feature-gate-unsized_fn_params.rs:17:8 | LL | fn foo(x: dyn Foo) { | ^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `(dyn Foo + '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) { | ~~~~ help: function arguments must have a statically known size, borrowed types always have a known size | LL | fn foo(x: &dyn Foo) { | + error[E0277]: the size for values of type `(dyn Foo + 'static)` cannot be known at compilation time --> $DIR/feature-gate-unsized_fn_params.rs:21:8 | LL | fn bar(x: Foo) { | ^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `(dyn Foo + 'static)` = help: unsized fn params are gated as an unstable feature help: you can use `impl Trait` as the argument type | LL | fn bar(x: impl Foo) { | ++++ help: function arguments must have a statically known size, borrowed types always have a known size | LL | fn bar(x: &Foo) { | + error[E0277]: the size for values of type `[()]` cannot be known at compilation time --> $DIR/feature-gate-unsized_fn_params.rs:25:8 | LL | fn qux(_: [()]) {} | ^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `[()]` = 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 qux(_: &[()]) {} | + error[E0277]: the size for values of type `(dyn Foo + 'static)` cannot be known at compilation time --> $DIR/feature-gate-unsized_fn_params.rs:29:9 | LL | foo(*x); | ^^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `(dyn Foo + 'static)` = note: all function arguments must have a statically known size = help: unsized fn params are gated as an unstable feature error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0277`.