src: simplify is_callable by making it a concept #58169
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tniessen
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Using a C++20 `concept` here makes `is_callable` much simpler than relying on SFINAE. It is equivalent for function types, `std::function`, lambdas, and classes with `operator()`, regardless of argument or return types.
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anonrig
reviewed
May 4, 2025
| @@ -111,7 +111,7 @@ struct CallLibuvFunction<ReqT, void(*)(ReqT*, Args...)> { | |||
| template <typename ReqT, typename T> | |||
| struct MakeLibuvRequestCallback { | |||
| static T For(ReqWrap<ReqT>* req_wrap, T v) { | |||
| static_assert(!is_callable<T>::value, | |||
| static_assert(!is_callable<T>, | |||
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You can change type name T to is_callable T and remove this static_assertion.
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #58169 +/- ##
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Coverage 90.13% 90.14%
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Files 630 630
Lines 186611 186611
Branches 36631 36634 +3
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+ Hits 168204 168220 +16
+ Misses 11192 11183 -9
+ Partials 7215 7208 -7
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jasnell
reviewed
May 7, 2025
| std::is_same<decltype(void(&T::operator())), void>::value | ||
| >::type> : std::true_type { }; | ||
| concept is_callable = | ||
| std::is_function<T>::value || requires { &T::operator(); }; |
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For concepts like this, I'd prefer if we adopted a naming scheme like IsCallable
jasnell
reviewed
May 7, 2025
| @@ -111,7 +111,7 @@ struct CallLibuvFunction<ReqT, void(*)(ReqT*, Args...)> { | |||
| template <typename ReqT, typename T> | |||
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Suggested change
| template <typename ReqT, typename T> | |
| template <typename ReqT, is_callable T> |
jasnell
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May 7, 2025
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| static_assert(!is_callable<T>, | ||
| "MakeLibuvRequestCallback missed a callback"); |
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Suggested change
| static_assert(!is_callable<T>, | |
| "MakeLibuvRequestCallback missed a callback"); |
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Using a C++20
concepthere makesis_callablemuch simpler than relying on SFINAE. It is equivalent for function types,std::function, lambdas, and classes withoperator(), regardless of argument or return types.