Saving selector to a variable

We have this solution:

// LESS
.selector {
    @r: ~'.selector';

    &--mode {
        @{r}__block {
            prop: value;
         }
    }
}

// CSS
.selector--mode .selector__block {
  prop: value;
}

I propose to add a feature: writing @r: &; instead of @r: ~".selector"; to get the current selector and save it in any variable.

Examples:

// LESS
.selector {
  @r: &; // .selector
}

.selector {
  &__inner {
    @r: &; // .selector__inner
  }
}

.selector {
  &--modification &__inner {
    @r: &; // .selector--modification .selector__inner
  }
}

Start by reviewing the existing selector and variable behavior against the LESS and CSS examples in the issue. Define completion as supporting the proposed @r: & forms for the three shown selector contexts, with tests confirming the documented results.