Twenty Twenty-One: style.css has errors in PhpStorm IDE

[mukesh27]

Hi, just upgraded to WP 5.6 with TwentyTwentyOne theme. The application itself seems to work fine. But when I open it with my PhpStorm IDE, the style.css file shows many errors. Most are related to many -- variables are not defined. But below caught my attention the most:

@media only screen and (min-width: 482px) {

	.primary-navigation > div > .menu-wrapper li {
		margin: 0;
		width: inherit;
	}

	.primary-navigation > div > .menu-wrapper li:last-child() {
		margin-right: 0;
	}
}

The IDE highlight last-child() as error. Why do we need a parenthesis here?

Original support ticket - ​https://wordpress.org/support/topic/twentytwentyone-theme-style-css-has-errors/

Props to @activecoder

[SergeyBiryukov]

Yeah, it looks like the brackets are not needed for ​:last-child, only for ​:nth-last-child.

[SergeyBiryukov]

In 49914:

Twenty Twenty-One: Remove extra brackets from :last-child CSS pseudo-class.

Props munyagu, mukesh27, activecoder.
Fixes #52176.