Implement parent selector

test/less/selectors.less

@@ -22,3 +22,27 @@ td {
 td, input {
   line-height: 1em;
 }
+
+a {
+  color: red;
+
+  &:hover { color: blue; }
+
+  div & { color: green; }
+
+  p & span { color: yellow; }
+}
+
+.foo {
+  .bar, .baz {
+    & .qux {
+      display: block;
+    }
+    .qux & {
+      display: inline;
+    }
+    .qux & .biz {
+      display: none;
+    }
+  }
+}