private static boolean checkOnlyDefaultConstructor(CtClass<?> ctClass) {
   Set<? extends CtConstructor<?>> constructors = ctClass.getConstructors();
   if (constructors.size() > 1) return false;
   if (constructors.isEmpty()) return true;
   CtConstructor<?> constructor = constructors.iterator().next();
   return constructor.isImplicit();
 }
  private static <T> void processConstructor(CtConstructor<T> c, CtClass<T> toMerge) {
    CtStatement firstStmt = c.getBody().getStatements().get(0);
    if (firstStmt instanceof CtInvocation) {
      CtInvocation<?> superConstructorCall = (CtInvocation) firstStmt;
      if (!(superConstructorCall.getExecutable().getDeclaration() instanceof CtConstructor)) return;
      CtConstructor superConstructor =
          (CtConstructor) superConstructorCall.getExecutable().getDeclaration();
      if (superConstructor.getDeclaringType() == toMerge) {
        CtBlock superConstructorBody = c.getFactory().Core().clone(superConstructor.getBody());
        superConstructorBody.accept(
            new CtScanner() {
              @Override
              public <T> void visitCtParameterReference(CtParameterReference<T> ref) {
                int parameterOrder = superConstructor.getParameters().indexOf(ref.getDeclaration());
                ref.setDeclaringExecutable(c.getReference());
                CtExpression<?> arg = superConstructorCall.getArguments().get(parameterOrder);
                if (!(arg instanceof CtVariableAccess))
                  throw sgce("super() should be directly called in " + c);
                CtVariable param = ((CtVariableAccess) arg).getVariable().getDeclaration();
                if (!(param instanceof CtParameter))
                  throw sgce("super() should be directly called in " + c);
                ref.setSimpleName(param.getSimpleName());

                super.visitCtParameterReference(ref);
              }
            });
        c.getBody().removeStatement(firstStmt);
        List<CtStatement> superConstructorBodyStatements = superConstructorBody.getStatements();
        for (int i = superConstructorBodyStatements.size() - 1; i >= 0; i--) {
          c.getBody().insertBegin(superConstructorBodyStatements.get(i));
        }
      }
    }
  }