NPE is expected but not thrown when the invocationName is null:
SwitchBootstraps.enumSwitch(
                MethodHandles.lookup(),
                null,
                MethodType.methodType(int.class, FooEnum.class, int.class),
                "FOO", "BAR", "BAZ");

Label takes entries that are not in names of enum constants:
        // enum FooEnum {FOO, BAR, BAZ, BING}
        CallSite callSite = SwitchBootstraps.enumSwitch(
                MethodHandles.lookup(),
                "_",
                MethodType.methodType(int.class, FooEnum.class, int.class),
                "A", "B");

Null string in label throws an IllegalArgumentException but not documented:
        // enum FooEnum {FOO, BAR, BAZ, BING}
        CallSite callSite = SwitchBootstraps.enumSwitch(
                MethodHandles.lookup(),
                "_",
                MethodType.methodType(int.class, FooEnum.class, int.class),
                "");