using hash_value() for in different namespace about describe HOT 2 CLOSED

This will work as-is under Boost 1.81, but if you need to support earlier versions, you have to define the overloads of hash_value in the corresponding namespace of the type. The easiest way to do it is to add a using declaration for your existing hash_value:

#if BOOST_VERSION < 108100
using ::hash_value;
#endif

after each BOOST_DESCRIBE_STRUCT, as in https://godbolt.org/z/M1n3Me7eY.

You can also put the common definition of hash_value into a namespace of your own, it doesn't need to be global.

(Unrelated, unless you're on C++20, you can also add using boost::describe::operator== and using boost::describe::operator!= to generate the equality operators, as these are generally required to use the hash containers.)

from describe.

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from describe.