error[E0520]: `from` specializes an item from a parent `impl`, but that item is not marked `default` --> $DIR/issue-111232.rs:6:5 | LL | fn from(s: S) -> S { | ^^^^^^^^^^^^^^^^^^ | = note: parent implementation is in crate `core` error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0520`.