code: function getShash() {
    const type = NodeType.ShashType;
    const token = tokens[pos];
    const line = token.ln;
    const column = token.col;
    const content = [];
  
    // Skip `#`.
    pos++;
  
    if (checkInterpolatedVariable(pos)) content.push(getInterpolatedVariable());
    else content.push(getIdent());
  
    return newNode(type, content, line, column);
  }
docs: Get node with a hexadecimal number (e.g. `#fff`) inside a simple
  selector
  @returns {Array} `['shash', x]` where `x` is a hexadecimal number
  converted to string (without `#`, e.g. `fff`)