public linear type without a public consumer

Why this fires¶

A pub @linear type has no public consumer: no code outside its module could ever use a value up, so every value would leak.

@linear
pub struct Handle { fd: int }
impl Handle {
  fn close(sink self) { ... }   // private: TE178 on `Handle`
}

Fix it¶

Make a consumer public, such as pub fn close(sink self).