Code shared from the Rust Playground

playground.rs

#![allow(unreachable_code)]


fn main() {
    println!("{:?}", {
        fn breed_cow<'a, 'b>(a: std::borrow::Cow<'a, str>) -> std::borrow::Cow<'b, str> { a.clone() }
    });
}


/* ~~~~=== stderr ===~~~~
   Compiling playground v0.0.1 (/playground)
error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
 --> src/main.rs:6:93
  |
6 |         fn breed_cow<'a, 'b>(a: std::borrow::Cow<'a, str>) -> std::borrow::Cow<'b, str> { a.clone() }
  |                                                                                             ^^^^^
  |
note: first, the lifetime cannot outlive the lifetime 'a as defined on the function body at 6:22...
 --> src/main.rs:6:22
  |
6 |         fn breed_cow<'a, 'b>(a: std::borrow::Cow<'a, str>) -> std::borrow::Cow<'b, str> { a.clone() }
  |                      ^^
  = note: ...so that the types are compatible:
          expected &std::borrow::Cow<'_, str>
             found &std::borrow::Cow<'a, str>
note: but, the lifetime must be valid for the lifetime 'b as defined on the function body at 6:26...
 --> src/main.rs:6:26
  |
6 |         fn breed_cow<'a, 'b>(a: std::borrow::Cow<'a, str>) -> std::borrow::Cow<'b, str> { a.clone() }
  |                          ^^
  = note: ...so that the expression is assignable:
          expected std::borrow::Cow<'b, _>
             found std::borrow::Cow<'_, _>

error: aborting due to previous error

error: Could not compile `playground`.

To learn more, run the command again with --verbose.

*/

/* ~~~~=== stdout ===~~~~

*/