1 error[E0308]: mismatched types
2 --> $DIR/universal-mismatched-type.rs:14:5
4 LL | fn foo(x: impl Debug) -> String {
5 | ------ expected `std::string::String` because of return type
6 LL | x //~ ERROR mismatched types
7 | ^ expected struct `std::string::String`, found type parameter
9 = note: expected type `std::string::String`
10 found type `impl Debug`
12 error: aborting due to previous error
14 For more information about this error, try `rustc --explain E0308`.