Static field update for switch over enums

[Johannes Aronsson]

ExtendJ 8.1.2-85-gcff2884 Java 9

When adding support for Java 9 and bytecode version 53 invalid bytecode for switch statements over enums is created. The error “Update to static final field” appears for the regression tests enum/switch_01p, enum/switch_02p and the following shortened example:

‌

public class Test {
  public static void main(String[] args) {
    Egg egg = Egg.TURKEY;
    System.out.format("%s egg weighs %dg", egg, weight(egg));
  }
  static int weight(Egg egg) {
    switch (egg) {
      case TURKEY:
        return 1000;
    }
    return -1;
  }
}
enum Egg {
  TURKEY,
}

Expected result: “TURKEY egg weighs 1000g”

Actual result:

Exception in thread "main" java.lang.IllegalAccessError: Update to static final field Test.$SwitchMap$Egg attempted from a different method ($SwitchMap$Egg) than the initializer method <clinit>
at Test.$SwitchMap$Egg(Test.java)
at Test.weight(Test.java:29)
at Test.test(Test.java:13)
at Test.main(Test.java:7)

This appears to be because of Java 9 being stricter about updates to final fields and javac creates an anonumous class to contain the SwitchMap which extendJ doesn’t do.

‌

[Jesper Öqvist]

It looks like javac generates switch maps in their own anonymous classes in Java 9+, that solution should work backwards for older Java versions as well.

[Jesper Öqvist]

Generate enum switch maps in anonymous classes

An implicit anonymous class is created for each enum switch map, this fixes incompatible code generating when generating bytecode for Java 9 or later versions (bytecode version 53.0+).

Changed the attribute TypeDecl.isAnonymous() from inherited to synthesized.

Added new subclass SwitchMapDecl of AnonymousDecl for enum switch map classes.

Fixes #318

→ <<cset dbd6240ff95c>>