While working on another feature, I noticed that a selector such as
`.foo::before` was parsed as:
```ts
[
{
kind: 'compound',
nodes: [
{ kind: 'selector', value: '.foo' },
{ kind: 'selector', value: ':' },
{ kind: 'selector', value: '::before' },
],
},
]
```
Instead of:
```ts
[
{
kind: 'compound',
nodes: [
{ kind: 'selector', value: '.foo' },
{ kind: 'selector', value: '::before' },
],
},
]
```
So far this hasn't been a real issue in practice, but it is in a
follow-up PR that I'm working on. To keep things separated, I wanted to
fix this behavior in a dedicated PR instead.
## Test plan
1. Added a test case for this situation
2. Other tests still pass
d03edefd19