css/selectors/parsing/parse-has-disallow-nesting-has-inside-has.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Selectors: The relational pseudo-class (disallow nesting :has() inside :has())</title>
<link rel="author" title="Byungwoo Lee" href="mailto:blee@igalia.com">
<link rel="help" href="https://drafts.csswg.org/selectors-4/#has-pseudo">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/css/support/parsing-testcommon.js"></script>
<script>
  test_invalid_selector('.a:has(.b:has(.c))');
  test(() => {
    // It's not easy to check that these are invalid because :is() and :where()
    // use forgiving parsing. Check that they never match instead.
    assert_false(document.documentElement.matches(":has(:is(:has(*)))"));
    assert_false(document.documentElement.matches(":has(:where(:has(*)))"));
    assert_true(document.documentElement.matches(":has(:is(:has(*), script))"));
    assert_true(document.documentElement.matches(":has(:where(:has(*), script))"));
  })
</script>