deduction guides for
Defined in header
reference_wrapper(T&) -> reference_wrapper<T>;
In C++17 this support is provided via the
reference_wrapper(T&) constructor, but that constructor is removed in C++20 in favor of a constructor template that does not support class template argument deduction, necessitating a separate deduction guide.
|This section is incomplete|
Reason: no example
 Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
|DR||Applied to||Behavior as published||Correct behavior|
|LWG 2981||C++17|| a redundant deduction guide from