| error[E0308]: mismatched types | |
| --> $DIR/universal-mismatched-type.rs:4:5 | |
| | | |
| LL | fn foo(x: impl Debug) -> String { | |
| | ---------- ------ expected `String` because of return type | |
| | | | |
| | found this type parameter | |
| LL | x | |
| | ^ expected `String`, found type parameter `impl Debug` | |
| | | |
| = note: expected struct `String` | |
| found type parameter `impl Debug` | |
| error: aborting due to 1 previous error | |
| For more information about this error, try `rustc --explain E0308`. |