96076.rs

use std::fmt;

trait MyTrait { }

/// warning: trait objects without an explicit `dyn` are deprecated
/// --> traits.rs:5:23
///    |
/// 5 | impl fmt::Display for MyTrait {
///    |                       ^^^^^^^
///        |
///    = note: `#[warn(bare_trait_objects)]` on by default
///        = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
///        = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
///    help: use `dyn`
///        |
///    5 - impl fmt::Display for MyTrait {
///        5 + impl fmt::Display for dyn MyTrait {
///            |
///
///            warning: 1 warning emitted
/*impl fmt::Display for MyTrait {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Hello here")
    }
}*/


/// error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
///    --> traits.rs:27:6
///    |
/// 27 | impl<T: MyTrait> fmt::Display for T {
///    |      ^ type parameter `T` must be used as the type parameter for some local type
///        |
///    = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
///        = note: only traits defined in the current crate can be implemented for a type parameter
///
///        error: aborting due to previous error
///        For more information about this error, try `rustc --explain E0210`.
impl<T: MyTrait> fmt::Display for T {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        todo!();
    }
}

fn main() { }