Issue extending selectors nested using "&"

[joshlasdin]

I often write "nested" selectors using the & to reference the base piece of the class (similar to BEM, SUIT, etc):

.testComponent {
  &-child { ... }
  &--variant { ... }
}

However, I've found that when I attempt to extend one of these "nested" selectors, it fails to compute correctly:

.foobar:extend(.testComponent-child) {}

I'm not sure if this is expected of the language, or not, but wanted to toss it out there to see if I should be doing something differently. I'd like to be able to extend these selectors without removing the convenience that "&" gives me when defining the selectors.

I've put together a simple CodePen showing the issue here: https://codepen.io/joshlasdin/pen/GEYmzV

Thanks!

[seven-phases-max]

See #2200.

[seven-phases-max]

Closing as duplicate of #2200.