Wrong tokenization of extended scss class names

[aeschli]

From @croccifixio on November 1, 2017 20:36

Steps to Reproduce:

1. Create a class rule in an SCSS file.
2. Extend the class using nesting and an &.
3. Begin the name of the extension to the class with 2 or more hyphens.

Based on the above screenshot, __element is tokenized as punctuation.definition.entity.css, which I suppose is alright.

However, --modifier is tokenized as variable.css which can lead to unsightly styling issues if the two tokens are styled differently in a particular theme (see the screenshot above).
Copied from original issue: microsoft/vscode#37444

[aeschli]

@croccifixio Would be great if you make your pull request here (thanks @maxibanki)

[adamreisnz]

Not sure if this is the right issue to post this, but there seem to be quite a few issues with incorrect scopes in the last version of language-sass when nesting;