& interpolation in selector causes segfault

[xzyfer]

This causes a segfault on the latest master.

.foo {
  [baz="#{&}"] {
    foo: bar;
  }
}

Results in

[1] 37755 segmentation fault sassc test.scss

/cc @ekskimn this may be of interest to you.

[ekskimn]

@xzyfer Taking a look....

[ekskimn]

@xzyfer Just a quick update....i did some debugging and the error occurs in the eval visitor when visiting the parent selector, after doing the contextualize visitation and before executing any of the listize visitations. It isn't in the static cast, because I broke that out into its own line and it got passed that just fine. Somehow it is blowing up when calling perform(listize) but not sure why yet.

[xzyfer]

I started looking at this last week. I've been bogged down this week but I think I'm close. I'll take a look this weekend.

[mgreter]

IMHO the bug occurs because fallback somewhere is returning parent which is null in this case. Bit I wasn't able to further debug into it, so not sure if this really is the problem. Edit: this is happening in Contextualize::fallback_impl.

[ekskimn]

@mgreter Thanks Marcel~! I didnt' get a chance to look at this further~!