ASTParser astParser = ASTParser.newParser(AST.JLS17);
    Map<String, String> options = new HashMap<>();
    options.put(JavaCore.COMPILER_COMPLIANCE, "17");
    options.put(JavaCore.COMPILER_SOURCE, "17");

    options.put(JavaCore.COMPILER_PB_ENABLE_PREVIEW_FEATURES, "enabled");

    astParser.setCompilerOptions(options);
    astParser.setEnvironment(new String[] {}, new String[] {}, new String[] {}, true);
    astParser.setUnitName("Example.java");
    astParser.setResolveBindings(true);
    astParser.setBindingsRecovery(true);

    String source =
      "sealed class A permits B, C {}\n"
      + "final class B extends A {}\n"
      + "non-sealed class C extends A {}";
    astParser.setSource(source.toCharArray());

    CompilationUnit compilationUnit = (CompilationUnit) astParser.createAST(null);
    TypeDeclaration a = (TypeDeclaration) compilationUnit.types().get(0);

    if (!Modifier.isSealed(a.getModifiers())) {
      throw new AssertionError("Modifier is not present in AST");
    }

    if (a.permittedTypes().size() != 2) {
      throw new AssertionError("permitted types are not present in AST");
    }

    ITypeBinding aBinding = a.resolveBinding();
    if (!Modifier.isSealed(aBinding.getModifiers())) {
      // permitted types not even available through the ITypeBinding interface
      throw new AssertionError("'sealed' modifier is not set in binding");
    }