Method expect

cranelift/isle/isle/src/parser.rs:62–71

(&mut self, f: F)

    }

    fn expect<F: Fn(&Token) -> bool>(&mut self, f: F) -> Result<Token> {
        if let Some(&(pos, ref peek)) = self.lexer.peek() {
            if !f(peek) {
                return Err(self.error(pos, format!("Unexpected token {peek:?}")));
            }
            Ok(self.lexer.next()?.unwrap().1)
        } else {
            Err(self.error(self.lexer.pos(), "Unexpected EOF".to_string()))
        }
    }

    fn eat<F: Fn(&Token) -> bool>(&mut self, f: F) -> Result<Option<Token>> {
        if let Some(&(_pos, ref peek)) = self.lexer.peek() {