error: expected one of `:`, `@`, or `|`, found `)` --> $DIR/param-attrs-2018.rs:3:41 | LL | trait Trait2015 { fn foo(#[allow(C)] i32); } | ^ expected one of `:`, `@`, or `|` | = note: anonymous parameters are removed in the 2018 edition (see RFC 1685) help: if this is a `self` type, give it a parameter name | LL | trait Trait2015 { fn foo(#[allow(C)] self: i32); } | +++++ help: if this is a parameter name, give it a type | LL | trait Trait2015 { fn foo(#[allow(C)] i32: TypeName); } | ++++++++++ help: if this is a type, explicitly ignore the parameter name | LL | trait Trait2015 { fn foo(#[allow(C)] _: i32); } | ++ error: aborting due to 1 previous error