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is_hashable is broken in C++20 (std::hash<T>::result_type and ::argument_type were removed) #602

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stevenwdv opened this issue Dec 19, 2023 · 0 comments · May be fixed by #603
Open

is_hashable is broken in C++20 (std::hash<T>::result_type and ::argument_type were removed) #602

stevenwdv opened this issue Dec 19, 2023 · 0 comments · May be fixed by #603

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@stevenwdv
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In C++ 20, e.g. rxu::is_hashable<std::string> unexpectedly returns false because std::hash<T>::result_type and ::argument_type were removed (cppreference, P0619R2). See definition of is_hashable:

RxCpp/Rx/v2/src/rxcpp/rx-util.hpp

Lines 1022 to 1028 in 761b932

template<typename T>
struct is_hashable<T,
typename rxu::types_checked_from<
typename filtered_hash<T>::result_type,
typename filtered_hash<T>::argument_type,
typename rxu::callable_result<filtered_hash<T>, T>::type>::type>
: std::true_type {};

This means functions like observable<T>::distinct() do not work anymore.
stevenwdv pushed a commit to stevenwdv/RxCpp that referenced this issue Jan 16, 2024
Fix C++20 compatibility
51299b5 
Closes ReactiveX#602
stevenwdv pushed a commit to stevenwdv/RxCpp that referenced this issue Jan 16, 2024
Fix C++20 compatibility
7dee3b8 
Closes ReactiveX#602
@stevenwdv stevenwdv linked a pull request Jan 16, 2024 that will close this issue
Open
stevenwdv pushed a commit to stevenwdv/RxCpp that referenced this issue Jan 25, 2024
Fix C++20 compatibility
2508fab 
Closes ReactiveX#602
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Fix C++20 compatibility for filtered_hash stevenwdv/RxCpp
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@stevenwdv