Interpolation inside an interpolation isn't handled correctly

[xzyfer]

The following results in an invalid property name error.

$foo: "bar";
%#{"foo--#{$foo}"} {
    foo: bar;
}

a { 
  @extend %foo--bar; 
}

I suspect this is partly responsible for #439 as well.

Specs added sass/sass-spec#123.

[lunelson]

Isn't this an interpolation inside an interpolation? The following works as far as I can tell

$foo: "bar";
%foo--#{$foo} {
    foo: bar;
}

a { 
  @extend %foo--bar; 
}

[xzyfer]

Yeah it essentially boils down to interpolation inside an interpolation. Updated the issue title accordingly. FTR this also works

$foo: "bar";
%#{"foo--" + $foo} {
    foo: bar;
}

a { 
  @extend %foo--bar; 
}

[ghost]

Created a pull request for this:

#854

[mgreter]

This should be solved by #910!