Should error on selector with invalid quote mark

[xzyfer]

Discovered from #2080

Sass

$prefix: "";
$suffix: bar;
$class: $prefix#{"-"}#{$suffix};

#{$class} {
  foo: bar;
}

LibSass 3.3.6

""-bar {
  foo: bar;
}

Ruby Sass 3.4.21

Invalid CSS after "": expected selector, was """-bar"

Spec added sass/sass-spec#912

[xzyfer]

A work around for this is Interpolating $prefix because interpolation should always return an unquoted string.

$class: #{$prefix}#{"-"}#{$suffix};

Produces

-bar {
  foo: bar;
}