[libcxx-commits] [PATCH] D128864: [libc++] Fix algorithms which use reverse_iterator

[Konstantin Varlamov via Phabricator via libcxx-commits]

var-const added inline comments.


================
Comment at: libcxx/include/__iterator/reverse_iterator.h:211
 #if _LIBCPP_STD_VER > 17
     requires requires {
       { __x.base() == __y.base() } -> convertible_to<bool>;
----------------
If we're doing essentially a workaround, would it be possible/easier to instead define an internal comparator for reverse iterators and use it in the affected algorithms?
```
bool __reverse_iter_eq(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y) {
  return __x.base() == __y.base();
}
// In the algorithm
for (; !std::__reverse_iter_eq(__first, __last); ++__first) {
```


================
Comment at: libcxx/include/__iterator/reverse_iterator.h:429
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const _AlgRevIter& __lhs, const _AlgRevIter& __rhs) {
+    return __lhs.base() == __rhs.base();
+  }
----------------
Hmm, so this expression is not ambiguous, but when it's used as a constraint in a `requires` clause, it is considered ambiguous? Am I missing something?


Repository:
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  https://reviews.llvm.org/D128864/new/

https://reviews.llvm.org/D128864