LearnBoost/stylus — Issue #541: Nested @extend results in repeated selectors
Author: ianstormtaylor
Created: 2012-01-27 16:24:30+00:00
State: open

I have:

```
body,
button,
input
couple: things

input
buncha: stuff

button
@extend input
more: stuff

.button
@extend button
```

And compiled CSS shows for the first block:

```
body,
button,
input,
button,
.button,
.button {
couple: things
}
```

Compiler should check to make sure the selector isn't already attached to blocks before being added.