Compiling playground v0.0.1 (/playground) error: lifetime in trait object type must be followed by `+` --> src/lib.rs:1:18 | 1 | fn x<'a>(x: &mut 'a i32){} | ^^ error: expected one of `:`, `@`, or `|`, found `)` --> src/lib.rs:1:24 | 1 | fn x<'a>(x: &mut 'a i32){} | ^ expected one of `:`, `@`, or `|` | = note: anonymous parameters are removed in the 2018 edition (see RFC 1685) help: if this was a parameter name, give it a type | 1 | fn x<'a>(x: &mut 'a i32: TypeName){} | ^^^^^^^^^^^^^ help: if this is a type, explicitly ignore the parameter name | 1 | fn x<'a>(x: &mut 'a _: i32){} | ^^^^^^ error: expected one of `)` or `,`, found `i32` --> src/lib.rs:1:21 | 1 | fn x<'a>(x: &mut 'a i32){} | -^^^ expected one of `)` or `,` | | | help: missing `,` warning: trait objects without an explicit `dyn` are deprecated --> src/lib.rs:1:18 | 1 | fn x<'a>(x: &mut 'a i32){} | ^^ help: use `dyn`: `dyn 'a` | = note: `#[warn(bare_trait_objects)]` on by default error[E0224]: at least one trait is required for an object type --> src/lib.rs:1:18 | 1 | fn x<'a>(x: &mut 'a i32){} | ^^ error: aborting due to 4 previous errors; 1 warning emitted For more information about this error, try `rustc --explain E0224`. error: could not compile `playground`. To learn more, run the command again with --verbose.