error[E0004]: non-exhaustive patterns: `box _` not covered --> $DIR/issue-3601.rs:30:44 | LL | box NodeKind::Element(ed) => match ed.kind { | ^^^^^^^ pattern `box _` not covered | note: `Box` defined here --> $SRC_DIR/alloc/src/boxed.rs:LL:COL = note: the matched value is of type `Box` help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown | LL ~ box ElementKind::HTMLImageElement(ref d) if d.image.is_some() => { true } LL + box _ => todo!() | error: aborting due to previous error For more information about this error, try `rustc --explain E0004`.