--- /dev/null
+// ignore-tidy-linelength
+#![feature(box_into_boxed_slice)]
+
+use std::boxed::Box;
+use std::fmt::Debug;
+fn main() {
+ let boxed_slice = Box::new([1,2,3]) as Box<[u8]>;
+ let _ = Box::into_boxed_slice(boxed_slice);
+ //~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
+ //~^^ ERROR the size for values of type `[u8]` cannot be known at compilation time
+ let boxed_trait: Box<dyn Debug> = Box::new(5u8);
+ let _ = Box::into_boxed_slice(boxed_trait);
+ //~^ ERROR the size for values of type `dyn std::fmt::Debug` cannot be known at compilation time
+ //~^^ ERROR the size for values of type `dyn std::fmt::Debug` cannot be known at compilation time
+}
--- /dev/null
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+ --> $DIR/box-into-boxed-slice-fail.rs:8:35
+ |
+LL | let _ = Box::into_boxed_slice(boxed_slice);
+ | ^^^^^^^^^^^ doesn't have a size known at compile-time
+ |
+ = help: the trait `std::marker::Sized` is not implemented for `[u8]`
+ = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
+ = note: required by `std::boxed::Box::<T>::into_boxed_slice`
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+ --> $DIR/box-into-boxed-slice-fail.rs:8:13
+ |
+LL | let _ = Box::into_boxed_slice(boxed_slice);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+ |
+ = help: the trait `std::marker::Sized` is not implemented for `[u8]`
+ = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
+ = note: slice and array elements must have `Sized` type
+
+error[E0277]: the size for values of type `dyn std::fmt::Debug` cannot be known at compilation time
+ --> $DIR/box-into-boxed-slice-fail.rs:12:35
+ |
+LL | let _ = Box::into_boxed_slice(boxed_trait);
+ | ^^^^^^^^^^^ doesn't have a size known at compile-time
+ |
+ = help: the trait `std::marker::Sized` is not implemented for `dyn std::fmt::Debug`
+ = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
+ = note: required by `std::boxed::Box::<T>::into_boxed_slice`
+
+error[E0277]: the size for values of type `dyn std::fmt::Debug` cannot be known at compilation time
+ --> $DIR/box-into-boxed-slice-fail.rs:12:13
+ |
+LL | let _ = Box::into_boxed_slice(boxed_trait);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+ |
+ = help: the trait `std::marker::Sized` is not implemented for `dyn std::fmt::Debug`
+ = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
+ = note: slice and array elements must have `Sized` type
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
--- /dev/null
+// run-pass
+#![feature(box_into_boxed_slice)]
+
+use std::boxed::Box;
+fn main() {
+ assert_eq!(Box::into_boxed_slice(Box::new(5u8)), Box::new([5u8]) as Box<[u8]>);
+ assert_eq!(Box::into_boxed_slice(Box::new([25u8])), Box::new([[25u8]]) as Box<[[u8; 1]]>);
+ let a: Box<[Box<[u8; 1]>]> = Box::into_boxed_slice(Box::new(Box::new([5u8])));
+ let b: Box<[Box<[u8; 1]>]> = Box::new([Box::new([5u8])]);
+ assert_eq!(a, b);
+}