A DESCRIPTION OF THE PROBLEM :
As of commit 2581935 src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java line 289 reads

```java
boolean constantsOnly = Stream.of(labels).allMatch(l -> enumClass.isAssignableFrom(EnumDesc.class));
```

where `enumClass` has previously been verified to be an enum class (as its name suggests). Therefore `constantsOnly` is always `false`. This prevents the optimization in lines 291-303 from taking any effect.

The optimization itself seems to contain a bug as well: it is described as

```java
//if (selector == null) return -1
//else if (idx == 0) return mappingArray[selector.ordinal()]; //mapping array created lazily
//else return "typeSwitch(labels)"
```

but implemented as

```java
//if (selector == null) return -1
//else if (idx == 0) return "typeSwitch(labels)"
//else return mappingArray[selector.ordinal()]; //mapping array created lazily
```

If it were not for the first issue, then the second issue would result in incorrect return values when the generated `MethodHandle` is called with a `restart` value other than zero.