fn parse_visibility(&mut self) -> Visibility {
        if self.eat_keyword(keywords::Pub) { Public }
        else if self.eat_keyword(keywords::Priv) { Private }
        else { Inherited }
    }
// parse visiility: PUB, PRIV, or nothing
parse visiility: PUB, PRIV, or nothing
parse visiility : PUB PRIV or nothing
fn parse_visibility(&mut self) -> Visibility {
        if self.eat_keyword(keywords::Pub) { Public }
        else if self.eat_keyword(keywords::Priv) { Private }
        else { Inherited }
    }
fn parse_visibility ( & mut self ) -> Visibility { if self . eat_keyword ( keywords :: Pub ) { Public } else if self . eat_keyword ( keywords :: Priv ) { Private } else { Inherited } }
parse visiility: PUB, PRIV, or nothing
parse visiility : PUB PRIV or nothing
&mut self
&mut self