fix: do not erroneously assume that the last node is a not selector

lib/rules/selector-not-notation/__tests__/index.js

@@ -68,6 +68,24 @@ testRule({
 			endLine: 1,
 			endColumn: 13,
 		},
+		{
+			code: ':not(.bar, .baz, .foo) .qux {}',
+			fixed: ':not(.bar):not(.baz):not(.foo) .qux {}',
+			message: messages.expected('simple'),
+			line: 1,
+			column: 1,
+			endLine: 1,
+			endColumn: 23,
+		},
+		{
+			code: ':not(.bar, .baz) .qux :not(.foo) {}',
+			fixed: ':not(.bar):not(.baz) .qux :not(.foo) {}',
+			message: messages.expected('simple'),
+			line: 1,
+			column: 1,
+			endLine: 1,
+			endColumn: 17,
+		},
 		{
 			code: ':not(a ,) {}',
 			fixed: ':not(a) {}',

lib/rules/selector-not-notation/index.js

@@ -130,6 +130,19 @@ const rule = (primary, _, context) => {
 	};
 };
 
+/**
+ * @param {Node[]} nodes
+ */
+const getLastConsecutiveNot = (nodes) => {
+	let i = 0;
+
+	for (; i < nodes.length; i++) {
+		if (!isNot(/** @type {Node} */ (nodes[i]))) break;
+	}
+
+	return nodes[i - 1];
+};
+
 /**
  * @param {Pseudo} not
  */
@@ -152,7 +165,9 @@ function fixSimple(not) {
 	not.nodes.push(firstSelector);
 
 	for (const s of simpleSelectors) {
-		const last = not.parent.last;
+		const last = getLastConsecutiveNot(not.parent.nodes);
+
+		assert(last);
 
 		not.parent.insertAfter(last, last.clone({ nodes: [s] }));
 	}