deduction guides for std::pair

Header: <utility>

One deduction guide is provided for std::pair to account for the edge cases missed by the implicit deduction guides, in particular, non-copyable arguments and array to pointer conversion.

# Declarations

template<class T1, class T2>
pair(T1, T2) -> pair<T1, T2>;

(since C++17)

# Example

#include <utility>
 
int main()
{
    int a[2], b[3];
    std::pair p{a, b}; // explicit deduction guide is used in this case
}