support comments. Add failing test case for when mixin call does not have parent selectors

test/less/import-silent.less

@@ -2,9 +2,8 @@
 @import (silent) url("css-3.less");
 @import (silent) url("media.less");
 /*
-  The media statements - 1 is invalid (no selector) and 1 is just a comment
-  We should band invalid media queries solving the 1st case and not treat comments as rules,
-  solving the 2nd issue.
+  The media statement above is invalid (no selector)
+  We should ban invalid media queries with properties and no selector?
 */
 @import (silent) url("import/import-silent.less");
 
@@ -12,6 +11,8 @@
   .z();
 }
 
+.zz();
+
 .visible:extend(.z all) {
   extend: test;
 }

test/less/import/import-silent.less

@@ -31,4 +31,13 @@
   .hidden {
     hidden: true;
   }
+}
+
+/* comment is not output */
+
+.zz {
+  .y {
+    pulled-in: yes;
+  }
+  /* comment pulled in */
 }