// run-pass #![allow(incomplete_features)] #![feature(unsized_locals, unsized_fn_params)] pub trait Foo { fn foo(self) -> String; } impl Foo for [char] { fn foo(self) -> String { self.iter().collect() } } impl Foo for str { fn foo(self) -> String { self.to_owned() } } impl Foo for dyn FnMut() -> String { fn foo(mut self) -> String { self() } } fn main() { let x = *(Box::new(['h', 'e', 'l', 'l', 'o']) as Box<[char]>); assert_eq!(&x.foo() as &str, "hello"); let x = Box::new(['h', 'e', 'l', 'l', 'o']) as Box<[char]>; assert_eq!(&x.foo() as &str, "hello"); let x = "hello".to_owned().into_boxed_str(); assert_eq!(&x.foo() as &str, "hello"); let x = *("hello".to_owned().into_boxed_str()); assert_eq!(&x.foo() as &str, "hello"); let x = "hello".to_owned().into_boxed_str(); assert_eq!(&x.foo() as &str, "hello"); let x = *(Box::new(|| "hello".to_owned()) as Box<dyn FnMut() -> String>); assert_eq!(&x.foo() as &str, "hello"); let x = Box::new(|| "hello".to_owned()) as Box<dyn FnMut() -> String>; assert_eq!(&x.foo() as &str, "hello"); }