error[E0637]: `'_` cannot be used here --> $DIR/E0637.rs:1:24 | LL | fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str { | ^^ `'_` is a reserved lifetime name error[E0106]: missing lifetime specifier --> $DIR/E0637.rs:1:62 | LL | fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str { | ------- ------- ^^ expected named lifetime parameter | = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `str1` or `str2` help: consider introducing a named lifetime parameter | LL | fn underscore_lifetime<'a, '_>(str1: &'a str, str2: &'a str) -> &'a str { | +++ ~~ ~~ ~~ error[E0637]: `&` without an explicit lifetime name cannot be used here --> $DIR/E0637.rs:13:13 | LL | T: Into<&u32>, | ^ explicit lifetime name needed here | help: consider introducing a higher-ranked lifetime here with `for<'a>` --> $DIR/E0637.rs:13:8 | LL | T: Into<&u32>, | ^ error: aborting due to 3 previous errors Some errors have detailed explanations: E0106, E0637. For more information about an error, try `rustc --explain E0106`.