Fixup

- missed `if constexpr`
- wrong order and comparison

Author: frederick-vs-ja

libcxx/include/__ranges/as_const_view.h

@@ -160,7 +160,7 @@ struct __fn : __range_adaptor_closure<__fn> {
     } else if constexpr (is_lvalue_reference_v<_Type> && constant_range<const _UType> && !view<_UType>) {
       return {__strategy::__const_is_constant_range,
               noexcept(ref_view(static_cast<const _UType&>(std::declval<_Type>())))};
-    } else if (requires { as_const_view(std::declval<_Type>()); }) {
+    } else if constexpr (requires { as_const_view(std::declval<_Type>()); }) {
       return {__strategy::__otherwise, noexcept(as_const_view(std::declval<_Type>()))};
     } else {
       return {__strategy::__none, false};

libcxx/test/std/iterators/const.iterators/iterator.pass.cpp

@@ -93,7 +93,7 @@ constexpr void test_basic_operations() {
   static_assert(noexcept(iter_move(first)) == noexcept(std::ranges::iter_move(first.base())));
   static_assert(noexcept(std::ranges::iter_move(first)) == noexcept(std::ranges::iter_move(first.base())));
 
-  for (auto it = first; it != last; ++it) {
+  for (auto it = first; it.base() != last.base(); ++it) {
     (void)*it;
     (void)it->x;
     (void)iter_move(it);
@@ -174,7 +174,7 @@ int main() {
     static_assert(std::is_constructible_v<ConstIt, It>);
     static_assert(std::is_convertible_v<It, ConstIt>);
     static_assert(std::is_constructible_v<ConstIt, const It&> == std::is_copy_constructible_v<It>);
-    static_assert(std::is_constructible_v<const It&, ConstIt> == std::is_copy_constructible_v<It>);
+    static_assert(std::is_convertible_v<const It&, ConstIt> == std::is_copy_constructible_v<It>);
   });
 
   test_p2836r1();

libcxx/test/std/ranges/range.adaptors/range.as.const/ctor.pass.cpp

@@ -42,8 +42,12 @@ concept IsImplicitlyConstructible = requires(void (&fun)(T), Args&&... args) { f
 static_assert(IsImplicitlyConstructible<std::ranges::as_const_view<DefaultConstructibleView>>);
 static_assert(!IsImplicitlyConstructible<std::ranges::as_const_view<NonDefaultConstructibleView>, int>);
 
-static_assert(std::is_constructible_v<std::ranges::as_const_view<DefaultConstructibleView>>, DefaultConstructibleView);
+static_assert(std::is_constructible_v<std::ranges::as_const_view<DefaultConstructibleView>, DefaultConstructibleView>);
+static_assert(
+    std::is_constructible_v<std::ranges::as_const_view<DefaultConstructibleView>, NonDefaultConstructibleView>);
 static_assert(!std::is_convertible_v<DefaultConstructibleView, std::ranges::as_const_view<DefaultConstructibleView>>);
+static_assert(
+    !std::is_convertible_v<DefaultConstructibleView, std::ranges::as_const_view<NonDefaultConstructibleView>>);
 
 constexpr bool test() {
   std::ranges::as_const_view<DefaultConstructibleView> view = {};