Enums should be annotated with @Immutable

[Mike Glazer]

What happened?

warning: [ImmutableEnumChecker] enums should be immutable: 'VectorFieldType' has field 'conjureType' of type 'com.palantir.tiles2.api.config.ConjureVectorFieldType', the declaration of type 'com.palantir.tiles2.api.config.ConjureVectorFieldType' is not annotated with @com.google.errorprone.annotations.Immutable

When I define a type:

public enum VectorFieldType {
  Number(ConjureVectorFieldType.NUMBER);

  private final ConjureVectorFieldType conjureType;

  VectorFieldType(ConjureVectorFieldType conjureType) {
    this.conjureType = conjureType;
  }
}

What did you want to happen?

The conjure generated enums should be annotated with @com.google.errorprone.annotations.Immutable if they truly are (they are).

[iamdanfox]

I'm actually a huge fan of that @immutable annotation, as I love how if your system is currently immutable all the way down, you can whack it on a class and then rest assured that nobody will sneakily add in some mutation without having to conspicuously take out the annotation!

PR up anyway: palantir/conjure-java#1086