LearnBoost/stylus — Issue #511: Extends don't unify
Author: chriseppstein
Created: 2012-01-11 22:36:19+00:00
State: open

Given a selector where the extension is already implicitly applied

```
.foo, button {
color: red;
}
.foo {
@extends button
}
```

You get this:

```
.foo,
button,
.foo {
color: #f00;
}
```

but you should also consider superselector cases like if `a.foo` extends `.bar` and `a` extends `.bar`, you don't need to perform first extend because it is a subset of a.