docs: void defineFields(ClassVisitor writer) {
      for (Variable var : allVariables) {
        var.maybeDefineField(writer);
      }
      if (currentCalleeField != null) {
        currentCalleeField.defineField(writer);
      }
      if (currentRendereeField != null) {
        currentRendereeField.defineField(writer);
      }
      if (currentAppendable != null) {
        currentAppendable.defineField(writer);
      }
    }