Problem
The current ifstream/ofstream API allows illogical mode combinations:
  std::ifstream f("data.txt", std::ios::out); // Compiles, but doesn't work
Modes are bitmasks, error-prone, and not checked at compile time.
The current std::ios::openmode is an unscoped bitmask with limited type safety and poor readability.
Proposal
This proposal introduces a strongly typed alternative using enum class Mode, enabling clearer semantics, safer combinations, and future extensibility.
auto f = open_file<Mode::read>("data.txt");
auto g = open_file<write | Mode ::binary>("log.bin");
Mode
The mode is now explicit and scoped, reducing ambiguity and improving code clarity. Bitwise combinations are supported via overloaded operators, and modes can be introspected or validated at compile-time.
The template parameter Mode uses an enum class for clarity and safety. :
enum class Mode : std::uint8_t {
    read = 0x01,
    write = 0x02,
    binary = 0x04,
    append = 0x08
};

Benefits

  * Compile-time safety
  * Clear intent
  * Modern C++ style
  * No breaking changes — this is a parallel API