can't extend a class created with nesting

[valan]

#1207 fixed extending selectors declared in nested format, but I am not able to extend a class that was built with nesting. for example:

input:

.button {
    border: 1px solid #000;
    &alt {
        background: red;
    }
}
.foo {
    &:extend(.buttonalt);
}

expected:

.button {
  border: 1px solid #000;
}
.buttonalt,
.foo {
  background: red;
}

actual:

.button {
  border: 1px solid #000;
}
.buttonalt {
  background: red;
}

I use long class names in an object oriented css approach and nesting helps generate those in an organized fashion, it would be nice to be able to extend those classes

[seven-phases-max]

See #1539.

[seven-phases-max]

Closing as duplicate of #1539.