error[E0005]: refutable pattern in `for` loop binding: `None` not covered
  --> $DIR/E0297.rs:4:9
   |
LL |     for Some(x) in xs {}
   |         ^^^^^^^ pattern `None` not covered
   |
note: `Option<i32>` defined here
  --> $SRC_DIR/core/src/option.rs:LL:COL
   |
LL | pub enum Option<T> {
   | ------------------
...
LL |     None,
   |     ^^^^ not covered
   = note: the matched value is of type `Option<i32>`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0005`.