What problem does this feature solve?

We use slot names that use a bracketed syntax (specifically for dynamic slot names) i.e. slot="[foo][bar]").

v-slot: currently supports slots names with square brackets, as long as they are not the first character of the slot name. i.e. v-slot:foo[bar]="scope" (works), but not v-slot:[foo][bar]="scope" (does not work)

HTML5 allows for custom attributes with square brackets in the attribute name, as long as they do not start with restricted characters. However, in the case of v-slot, the attribute starts with v, so slot names that start with [ should work as expected (i.e. v-slot:[foo.bar] or v-slot:[foo][bar])

Using the deprecated slot="[foo]" syntax works as expected.

What does the proposed API look like?

v-slot adds support for slot names that start with a [, such as v-slot:[foo][bar]="scope"

There is no actual change to the API from the user perspective, just a change to the underlying code.

My guess that this is an issue with Vue template compiler:

From the template compiler on the Vuejs.org site (https://vuejs.org/v2/guide/render-function.html#Template-Compilation):

Does not work:

Does Work: