Additions to T.144: Don’t specialize function templates

T.144: Don’t specialize function templates

Example

template<typename T>
string stringify(const T& x) { to_string(x); }

template<> // bad, could be overload instead,
           // primary template forces us to pass string_view by const&
string stringify(const string_view& x) { return string(x); }

// better, non-template overload with improved signature
string stringify(string_view x) { return string(x); }

// alternative: "specialize" inside a single function using constexpr if-statement
template<typename T>
string stringify2(const T& x) {
    if constexpr (is_convertible_v<const T, string_view>) { return string(x); }
    else { return to_string(x); }
}

Alternatives

• if constexpr to provide alternative implementations within a function

Start with the existing T.144 guideline and review the supplied examples and Alternatives section for consistency with its current wording. Done means incorporating the requested guidance on overloads and constexpr if without changing the rule's intent; no file or test is named in the issue.