Babel implements multiple variants of this proposal to help TC39 test and gather feedback from the community. As with all proposals, expect changes in the future.

The simple problem that I see with fragment identifiers is that their existence and functionality relies completely on the developer rather than the browser. Yes, the browser needs to read and interpret the identifier and identify the matching fragment. But if the developer doesn’t include any id attributes in the HTML of the page, then there will be no identifiable fragments. Do you see why this is a problem? Whether the developer has coded identifiers into the HTML has nothing to do with whether or not the page actually has fragments. Virtually every web page has fragments. In fact, sectioning content as defined in the HTML5 spec implies as much. Every element on the page that can contain content can theoretically be categorized as a “fragment”.

proposes adding a grid-cell pseudo so you can add (responsive) decorative elements to grids without having to add empty elements to your page.

#grid::grid-area(1 / 2 / 3 / 4) { background-color: red;

Another possible syntax is {#slot bar}<Foo/>{/slot}, which would also allow a bunch of DOM nodes and components inside the slot, without them needing to be from a single component

I'm suggesting there should be a way to write lifecycle related code that also responds to changing props, like how useEffect works. I think how React handles this could be a good source of inspiration.

Syntax-wise, I would like to be able to pass id, style and class DOM attributes as well as (ideally) svelte props to whatever the slot was replaced with, so prefixing everything with attr in the slot that should be passed sounds like a good idea. Examples: <slot attr:class=“test” attr:class:active={true} /> or <slot attr:style=“color: red” attr:id=“henlo” />

Sometimes, the line between 'bug' and 'feature' is a hard one to draw. Generally, a feature is anything that adds new behavior, while a bug is anything that causes incorrect behavior. Sometimes, the core team will have to make a judgment call.