code: func (r *importReader) readString() {
  	switch r.nextByte(true) {
  	case '`':
  		for r.err == nil {
  			if r.nextByte(false) == '`' {
  				break
  			}
  			if r.eof {
  				r.syntaxError()
  			}
  		}
  	case '"':
  		for r.err == nil {
  			c := r.nextByte(false)
  			if c == '"' {
  				break
  			}
  			if r.eof || c == '\n' {
  				r.syntaxError()
  			}
  			if c == '\\' {
  				r.nextByte(false)
  			}
  		}
  	default:
  		r.syntaxError()
  	}
  }
docs: // readString reads a quoted string literal from the input.
  // If an identifier is not present, readString records a syntax error.