fix: do not reuse a pseudo's name as the namespace of a following |

src/__tests__/namespaces.mjs

@@ -201,3 +201,23 @@ throws("lone pipe symbol with trailing spaces", "| ");
 throws("lone pipe symbol with surrounding spaces", " | ");
 throws("trailing pipe symbol with a namespace", "foo| ");
 throws("trailing pipe symbol with any namespace", "*| ");
+
+test("`|` after a pseudo-class does not reuse its name as a namespace", "a:hover|b", (t, tree) => {
+  t.deepEqual(tree.nodes[0].nodes.length, 3);
+  t.deepEqual(tree.nodes[0].nodes[1].type, "pseudo");
+  t.deepEqual(tree.nodes[0].nodes[1].value, ":hover");
+  t.deepEqual(tree.nodes[0].nodes[2].type, "tag");
+  t.deepEqual(tree.nodes[0].nodes[2].namespace, true);
+  t.deepEqual(tree.nodes[0].nodes[2].value, "b");
+});
+
+test(
+  "`|*` after a pseudo-element does not reuse its name as a namespace",
+  "::before|*",
+  (t, tree) => {
+    t.deepEqual(tree.nodes[0].nodes.length, 2);
+    t.deepEqual(tree.nodes[0].nodes[0].value, "::before");
+    t.deepEqual(tree.nodes[0].nodes[1].type, "universal");
+    t.deepEqual(tree.nodes[0].nodes[1].namespace, true);
+  },
+);

src/parser.js

@@ -649,7 +649,10 @@ export default class Parser {
 
   combinator() {
     if (this.content() === "|") {
-      return this.namespace();
+      // A word or `*` right before this `|` was already consumed by whatever
+      // came before, such as the name of a pseudo in `:hover|a`, so it cannot be
+      // the prefix. Only a skipped `&` can still be one.
+      return this.namespace(false);
     }
     // We need to decide between a space that's a descendant combinator and meaningless whitespace at the end of a selector.
     let nextSigTokenPos = this.locateNextMeaningfulToken(this.position);
@@ -831,15 +834,18 @@ export default class Parser {
     return this.error(`Unexpected '|'.`, this.currToken[TOKEN.START_POS]);
   }
 
-  namespace() {
+  /**
+   * @param {boolean} [prefixed] whether the token before the `|` is still
+   *   unconsumed, as it is when `word()` or `universal()` sees the `|` next.
+   */
+  namespace(prefixed = true) {
     const prev = this.prevToken;
     // Only treat the previous token as a namespace prefix when it can actually
     // be one (a type/word or the universal `*`). A comment, comma, combinator
     // or whitespace before `|` means an empty namespace, not a prefix.
     const before =
       prev &&
-      (prev[TOKEN.TYPE] === tokens.word ||
-        prev[TOKEN.TYPE] === tokens.asterisk ||
+      ((prefixed && (prev[TOKEN.TYPE] === tokens.word || prev[TOKEN.TYPE] === tokens.asterisk)) ||
         prev[TOKEN.TYPE] === tokens.ampersand)
         ? this.content(prev)
         : true;