* s/__i/__prev/ in __is_sorted_until()

* remove bogus __libcpp_is_constant_evaluated() check in __set_intersection()
* change comment about checking number of steps in debug mode
* s/_LIBCPP_ASSERT_SEMANTIC_REQUIREMENT/_LIBCPP_ASSERT_INTERNAL/ for input validation

Author: ichaer

libcxx/include/__algorithm/is_sorted_until.h

@@ -24,11 +24,11 @@ template <class _Compare, class _ForwardIterator, class _Sent>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 __is_sorted_until(_ForwardIterator __first, _Sent __last, _Compare&& __comp) {
   if (__first != __last) {
-    _ForwardIterator __i = __first;
+    _ForwardIterator __prev = __first;
     while (++__first != __last) {
-      if (__comp(*__first, *__i))
+      if (__comp(*__first, *__prev))
         return __first;
-      __i = __first;
+      __prev = __first;
     }
   }
   return __first;

libcxx/include/__algorithm/set_intersection.h

@@ -99,12 +99,10 @@ __set_intersection(
     std::forward_iterator_tag,
     std::forward_iterator_tag) {
 #if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
-  if (!__libcpp_is_constant_evaluated()) {
-    _LIBCPP_ASSERT_INTERNAL(
-        std::__is_sorted_until(__first1, __last1, __comp) == __last1, "set_intersection: input range 1 must be sorted");
-    _LIBCPP_ASSERT_INTERNAL(
-        std::__is_sorted_until(__first2, __last2, __comp) == __last2, "set_intersection: input range 2 must be sorted");
-  }
+  _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
+      std::__is_sorted_until(__first1, __last1, __comp) == __last1, "set_intersection: input range 1 must be sorted");
+  _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
+      std::__is_sorted_until(__first2, __last2, __comp) == __last2, "set_intersection: input range 2 must be sorted");
 #endif
   _LIBCPP_CONSTEXPR std::__identity __proj;
   bool __prev_may_be_equal = false;

libcxx/test/std/algorithms/alg.sorting/alg.set.operations/set.intersection/set_intersection_complexity.pass.cpp

@@ -43,7 +43,7 @@
 
 #include "test_iterators.h"
 
-// Debug mode provides no complexity guarantees, testing them would be a waste of effort.
+// We don't check number of operations in Debug mode because they are not stable enough due to additional validations.
 #ifdef _LIBCPP_HARDENING_MODE_DEBUG
 #  define ASSERT_COMPLEXITY(expression) (void)(expression)
 #else