error[E0277]: the size for values of type `Self` cannot be known at compilation time --> $DIR/issue-27078.rs:3:12 | LL | fn foo(self) -> &'static i32 { | ^^^^ doesn't have a size known at compile-time | = help: unsized fn params are gated as an unstable feature help: consider further restricting `Self` | LL | fn foo(self) -> &'static i32 where Self: Sized { | +++++++++++++++++ help: function arguments must have a statically known size, borrowed types always have a known size | LL | fn foo(&self) -> &'static i32 { | + error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.