Method is

cranelift/isle/isle/src/parser.rs:84–90

(&self, f: F)

    }

    fn is<F: Fn(&Token) -> bool>(&self, f: F) -> bool {
        if let Some((_, peek)) = self.lexer.peek() {
            f(peek)
        } else {
            false
        }
    }

    fn pos(&self) -> Pos {
        if !self.disable_pos {