--- /dev/null
+/* @flow */
+"use strict";
+
+/**
+ * Check whether a at-rule is standard
+ *
+ * @param {atRule} postcss at-rule node
+ * @return {boolean} If `true`, the declaration is standard
+ */
+module.exports = function(atRule /*: postcss$atRule*/) /*: boolean*/ {
+ // Ignore scss `@content` inside mixins
+ if (!atRule.nodes && atRule.params === "") {
+ return false;
+ }
+
+ // Ignore detached ruleset `@detached-ruleset: { background: red; }; .top { @detached-ruleset(); }`
+ if (
+ !atRule.nodes &&
+ atRule.raws.afterName === "" &&
+ atRule.params[0] === "("
+ ) {
+ return false;
+ }
+
+ return true;
+};