$ javac  broken/PreviewWithoutFlag.java     (21.0.12.1)
broken/PreviewWithoutFlag.java:3: error: string templates are a preview feature and are disabled by default.
    public static void main(String[] args) { String n = "x"; System.out.println(STR."hi \{n}"); }
                                                                                    ^
  (use --enable-preview to enable string templates)
1 error

$ javac  broken/NonExhaustive.java     (21.0.12.1)
broken/NonExhaustive.java:6: error: the switch expression does not cover all possible input values
    static String f(S s) { return switch (s) { case A a -> "a"; }; }
                                  ^
1 error

$ javac  broken/DominatedCase.java     (21.0.12.1)
broken/DominatedCase.java:3: error: this case label is dominated by a preceding case label
    static String f(Object o) { return switch (o) { case CharSequence cs -> "cs"; case String s -> "s"; default -> "d"; }; }
                                                                                       ^
1 error