[libcxx-commits] [libcxx] [libc++][ranges] P2387R3: Pipe support for user-defined range adaptors (PR #89148)

[Xiaoyang Liu via libcxx-commits]

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@@ -52,15 +54,21 @@ struct __range_adaptor_closure_t : _Fn, __range_adaptor_closure<__range_adaptor_
 _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(__range_adaptor_closure_t);
 
 template <class _Tp>
-concept _RangeAdaptorClosure = derived_from<remove_cvref_t<_Tp>, __range_adaptor_closure<remove_cvref_t<_Tp>>>;
+_Tp __derived_from_range_adaptor_closure(__range_adaptor_closure<_Tp>*);
 
 template <class _Tp>
+concept _RangeAdaptorClosure = !ranges::range<remove_cvref_t<_Tp>> && requires {
+  { __derived_from_range_adaptor_closure((remove_cvref_t<_Tp>*)nullptr) } -> same_as<remove_cvref_t<_Tp>>;
+};
+
+template <class _Tp>
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xiaoyang-sde wrote:

It seems that `operator|(_Range&& __range, _Closure&& __closure)` requires `invocable<_Closure, _Range>`. Therefore, if `t` is not a unary function object that accepts a range argument, this constraint won't be satisfied, thus the compiler can't find a suitable `operator|`, resulting in a hard error.

https://github.com/llvm/llvm-project/pull/89148