[Sass] Don't die on interpolation in unrecognized selectors either.

doc-src/SASS_CHANGELOG.md

@@ -7,7 +7,7 @@
 
 [Tagged on GitHub](http://github.com/nex3/haml/commit/3.0.17).
 
-* Disallow `#{}` interpolation in `@media` queries.
+* Disallow `#{}` interpolation in `@media` queries or unrecognized directives.
   This was never allowed, but now it explicitly throws an error
   rather than just producing invalid CSS.
 

lib/sass/scss/css_parser.rb

@@ -7,6 +7,15 @@ module Sass
     # parent references, nested selectors, and so forth.
     # It does support all the same CSS hacks as the SCSS parser, though.
     class CssParser < StaticParser
+      # Parse a selector, and return its value as a string.
+      #
+      # @return [String, nil] The parsed selector, or nil if no selector was parsed
+      # @raise [Sass::SyntaxError] if there's a syntax error in the selector
+      def parse_selector_string
+        init_scanner!
+        str {return unless selector}
+      end
+
       private
 
       def parent_selector; nil; end

lib/sass/scss/parser.rb

@@ -109,11 +109,10 @@ module Sass
           return dir
         end
 
-        val = str do
-          # Most at-rules take expressions (e.g. @import),
-          # but some (e.g. @page) take selector-like arguments
-          expr || selector
-        end
+        # Most at-rules take expressions (e.g. @import),
+        # but some (e.g. @page) take selector-like arguments
+        val = str {break unless expr}
+        val ||= CssParser.new(@scanner, @line).parse_selector_string
         node = node(Sass::Tree::DirectiveNode.new("@#{name} #{val}".strip))
 
         if tok(/\{/)

test/sass/scss/scss_test.rb

@@ -1013,6 +1013,16 @@ MESSAGE
 SCSS
   end
 
+  def test_no_interpolation_in_unrecognized_directives
+    assert_raise(Sass::SyntaxError, <<MESSAGE) {render <<SCSS}
+Invalid CSS after "@foo ": expected selector or at-rule, was "\#{100} {"
+MESSAGE
+@foo \#{100} {
+  foo {bar: baz}
+}
+SCSS
+  end
+
   # Regression
 
   def test_weird_added_space