I was hoping the new CSS syntax for nesting would work just like in Sass, simple and intuitive. Unfortunately, it's apparently too ambiguous and inefficient for parsing.
> Nesting style rules naively inside of other style rules is, unfortunately, ambiguous—the syntax of a selector overlaps with the syntax of a declaration..
> It is, in most cases, eventually possible to tell properties and selectors apart, but doing so requires unbounded lookahead in the parser; that is, the parser might have to hold onto an unknown amount of content before it can tell which way it’s supposed to be interpreting it.
> CSS to date requires only a small, known amount of lookahead in its parsing, which allows for more efficient parsing algorithms, so unbounded lookahead is generally considered unacceptable among browser implementations of CSS.
> Nesting style rules naively inside of other style rules is, unfortunately, ambiguous—the syntax of a selector overlaps with the syntax of a declaration..
> It is, in most cases, eventually possible to tell properties and selectors apart, but doing so requires unbounded lookahead in the parser; that is, the parser might have to hold onto an unknown amount of content before it can tell which way it’s supposed to be interpreting it.
> CSS to date requires only a small, known amount of lookahead in its parsing, which allows for more efficient parsing algorithms, so unbounded lookahead is generally considered unacceptable among browser implementations of CSS.
https://drafts.csswg.org/css-nesting/#nesting