Method expect

compiler/src/modules/packages/manifest.rs:114–116

(&mut self, c: u8, msg: &'static str)

    }

    fn expect(&mut self, c: u8, msg: &'static str) -> Result<(), String> {
        if self.peek() == Some(c) { self.pos += 1; Ok(()) } else { Err(s!(str msg)) }
    }

    fn read_string(&mut self) -> Result<String, String> {
        self.expect(b'"', "expected '\"' starting a string")?;