error[E0407]: method `from` is not a member of trait `Fn` --> $DIR/issue-87558.rs:6:5 | LL | fn from() {} | ^^^^^^^^^^^^ not a member of trait `Fn` error[E0183]: manual implementations of `Fn` are experimental --> $DIR/issue-87558.rs:3:6 | LL | impl Fn(&isize) for Error { | ^^^^^^^^^^ manual implementations of `Fn` are experimental | = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable error[E0229]: associated type bindings are not allowed here --> $DIR/issue-87558.rs:3:6 | LL | impl Fn(&isize) for Error { | ^^^^^^^^^^ associated type not allowed here | help: parenthesized trait syntax expands to `Fn<(&isize,), Output=()>` --> $DIR/issue-87558.rs:3:6 | LL | impl Fn(&isize) for Error { | ^^^^^^^^^^ error: aborting due to 3 previous errors Some errors have detailed explanations: E0183, E0229, E0407. For more information about an error, try `rustc --explain E0183`.