feat: allow generics with SuperBuilder customization

[ntroutman]

Trying to customize @SuperBuilder for classes that contain generics will fail due to a check in javac/handlers/HandleSuperBuilder.constructorExists assuming that the only generics on the builder are the ones introduced by the builder itself. This means attempting to do:

@SuperBuilder
public class Parent<T> {
  int field;

  protected Parent(ParentBuilder<T, ?, ?> b) {
    if (b.field == 0)
      throw new IllegalArgumentException("field must be != 0");
      this.field = b.field;
    }
}

Lombok fails with the error error: constructor Parent(ParentBuilder<T,?,?>) is already defined in class Parent

[janrieke]

Let me know if you need any support, e.g. a intermediate review etc.

[janrieke]

The code before was not optimal already, as String comparisons tend to break quickly. Imagine something like Java extending the diamond operator also for ?, so that you can write:
protected Parent(ParentBuilder<> b) {...}
Thus, we should use the opportunity to improve it. I suggest doing an instanceof check and only use the generic toString as a fallback:

String typeName;
JCTree paramType = md.params.get(0).getType();
if (paramType instanceof JCTypeApply) {
	typeName = ((JCTypeApply)paramType).clazz.toString();
} else {
	typeName = paramType.toString();
}
int lastIndexOfDot = typeName.lastIndexOf('.');
if (lastIndexOfDot >= 0) {
	typeName = typeName.substring(lastIndexOfDot+1);
}
if (builderClassName.equals(typeName))
	return true;

[ntroutman]

Thanks, I'll work on that. I won't like have a chance until a couple weeks from now.

[rzwitserloot]

Yeah, using toString() to compare generics is a nono, though I find the idea of falling back on that in case a series of instanceof fails a great idea. @ntroutman still working on it, or?