There's a std::convertible_to<T> concept to check whether a result of a call can be converted to a certain type.
But I want to check if a function has an exact return-type. How can I do that?
How to check a function has an exact return-type using Concept?
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1 Answers
You can write a concept which uses the std::same_as to check the return type of the function:
Example:
#include <concepts> // std::same_as
template<typename FuncType, typename RetType>
concept SameReturn = requires(FuncType func) {
{ func() } -> std::same_as<RetType>;
};
template<typename Callable> requires SameReturn<Callable, int>
auto test(Callable func)
{
return func();
}
int main()
{
std::cout << test([]() {return 1; });
// std::cout << test([]() {return "string literals"; }); // error!
return 0;
}
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