C++17类模板实参推导的可读性问题及改进方案问询

Great question—this is a valid and widely shared concern among developers who want to balance modern C++ convenience with code clarity, especially for template-heavy types like custom tuple-like classes. Let’s break down the answers to your questions:

Are there existing proposals to solve this readability issue? #

Yes, several proposals have targeted improving the readability and explicitness of CTAD, with some already making their way into the standard:

• C++20 Partial Explicit Template Arguments: The proposal P1814R0: Explicit Template Arguments for Class Template Deduction was adopted into C++20, allowing you to explicitly specify some template arguments while letting the compiler deduce the rest. For example:

  // Explicitly specify the first type, let the compiler deduce the second
  Myple<int> t(42, "hello");
  

  This gives readers a clear hint about the type structure without forcing you to write every template argument manually.

• Proposals for Enhanced Explicitness: There have been discussions (like P2308R0 and related papers) around adding syntax to explicitly denote deduced types or enforce explicit template arguments in certain contexts, though none have been standardized yet. These aim to give developers more control over when CTAD is allowed vs. when explicit arguments are required.

Enforcing explicit template arguments in your code today #

If you want to mandate that users write Myple<...> t1(1); instead of relying on CTAD, you can disable CTAD for your class by deleting the implicit deduction guide:

template<typename T>
struct Myple {
    Myple(T val) : value(val) {}
    T value;
};

// Delete the implicit deduction guide to force explicit template arguments
template<typename T> Myple(T) -> Myple<T> = delete;

Now, any attempt to write Myple t(1); will trigger a compilation error, requiring the user to explicitly specify Myple<int> t(1); instead. This directly addresses your concern by making the template type visible in the code.

Final thoughts #

While CTAD is a powerful convenience feature, it’s totally reasonable to prioritize readability for types where the template arguments carry critical semantic meaning. The C++ standard has evolved to offer more flexibility here, and you can already enforce explicit arguments in your codebase using the deduction guide deletion trick above.

内容的提问来源于stack exchange，提问作者Alek86