function shouldHaveNewlines(expression, hasLeftNewline) {
      const isMultiline = expression.loc.start.line !== expression.loc.end.line;

      switch (isMultiline ? option.multiline : option.singleline) {
        case 'forbid': return false;
        case 'require': return true;
        case 'consistent':
        default: return hasLeftNewline;
      }
    }
Determines whether there should be newlines inside curlys
@param {ASTNode} expression The expression contained in the curlys
@param {boolean} hasLeftNewline `true` if the left curly has a newline in the current code.
@returns {boolean} `true` if there should be newlines inside the function curlys