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std::reference_wrapper::reference_wrapper

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template< class U >
reference_wrapper( U&& x ) noexcept(/*see below*/) ;
(1)
reference_wrapper( const reference_wrapper& other ) noexcept;
(2)

Constructs a new reference wrapper.

1) Converts x to T& as if by T& t = std::forward<U>(x);, then stores a reference to t. This overload only participates in overload resolution if typename std::decay<U>::type is not the same type as reference_wrapper and the expression FUN(std::declval<U>()) is well-formed, where FUN names the set of imaginary functions
void FUN(T&) noexcept;
void FUN(T&&) = delete;
2) Copy constructor. Stores a reference to other.get().

[edit] Parameters

x - an object to wrap
other - another reference wrapper

[edit] Exceptions

1)
noexcept specification:  
noexcept(noexcept(FUN(std::declval<U>())))
where FUN is the set of imaginary functions described in the description above.

[edit] 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 2993 C++11 deleted reference_wrapper(T&&) constructor interferes with overload resolution in some cases replaced with a constructor template