private static @Nullable PsiType getReturnType(PsiClass psiClass, MethodSignature methodSignature) {
    final PsiMethod method = getMethod(psiClass, methodSignature);
    if (method != null) {
      final PsiClass containingClass = method.getContainingClass();
      if (containingClass == null) return null;
      return TypeConversionUtil.getSuperClassSubstitutor(containingClass, psiClass, PsiSubstitutor.EMPTY).substitute(method.getReturnType());
    }
    else {
      return null;
    }
  }
private static @Nullable PsiType getReturnType(PsiClass psiClass, MethodSignature methodSignature)