at-root with nothing contains super selector

src/atrule/mod.rs

@@ -126,6 +126,20 @@ impl AtRule {
                             styles.push(s);
                             None
                         }
+                        Stmt::RuleSet(RuleSet {
+                            selector: mut selector2,
+                            rules,
+                            super_selector: super_selector2,
+                        }) => {
+                            if selector.is_empty() {
+                                selector2 = Selector::replace(super_selector.clone(), selector2);
+                            }
+                            Some(Stmt::RuleSet(RuleSet {
+                                selector: selector2,
+                                rules,
+                                super_selector: super_selector2,
+                            }))
+                        }
                         _ => Some(s),
                     })
                     .collect::<Vec<Stmt>>();

src/selector/mod.rs

@@ -18,16 +18,6 @@ mod attribute;
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub(crate) struct Selector(Vec<SelectorPart>);
 
-impl Selector {
-    pub const fn new() -> Selector {
-        Selector(Vec::new())
-    }
-
-    pub fn contains_super_selector(&self) -> bool {
-        self.0.iter().any(|s| s.contains_super_selector)
-    }
-}
-
 #[derive(Clone, Debug, Eq, PartialEq)]
 struct SelectorPart {
     pub inner: Vec<SelectorKind>,
@@ -543,4 +533,12 @@ impl Selector {
     pub fn is_empty(&self) -> bool {
         self.0.is_empty()
     }
+
+    pub const fn new() -> Selector {
+        Selector(Vec::new())
+    }
+
+    pub fn contains_super_selector(&self) -> bool {
+        self.0.iter().any(|s| s.contains_super_selector)
+    }
 }

tests/at-root.rs

@@ -33,3 +33,8 @@ test!(
     ".foo {\n  @at-root .bar {\n    a: b;\n    c {\n      d: e;\n      foo {\n        bar: baz;\n      }\n      h: j;\n    }\n    f: g;\n  }\n}\n",
     ".bar {\n  a: b;\n  f: g;\n}\n.bar c {\n  d: e;\n  h: j;\n}\n.bar c foo {\n  bar: baz;\n}\n"
 );
+test!(
+    super_selector_inside_with_nothing,
+    "foo {\n  @at-root {\n    & {\n      color: bar;\n    }\n  }\n}\n",
+    "foo {\n  color: bar;\n}\n"
+);