`string_view` must be `is_trivially_move_constructible_v` (#2128)

Co-authored-by: frederick-vs-ja <de34@live.cn>
Co-authored-by: Adam Bucior <35536269+AdamBucior@users.noreply.github.com>
Co-authored-by: Casey Carter <cartec69@gmail.com>

stl/inc/xstring

@@ -1274,8 +1274,10 @@ public:
 
 #if _HAS_CXX23
     // clang-format off
-    template <_RANGES contiguous_range _Range>
-        requires (_RANGES sized_range<_Range>
+    template <class _Range>
+        requires (!same_as<remove_cvref_t<_Range>, basic_string_view> // per LWG issue filed on 2021-08-16
+            && _RANGES contiguous_range<_Range>
+            && _RANGES sized_range<_Range>
             && same_as<_RANGES range_value_t<_Range>, _Elem>
             && (!is_convertible_v<_Range, const _Elem*>)
             && (!requires(remove_cvref_t<_Range>& _Rng) {

tests/std/tests/P0220R1_string_view/test.cpp

@@ -74,6 +74,19 @@ const evil_conversion_to_string_view_lvalue_only convert_lvalue_only{};
 static_assert(is_trivially_copyable_v<string_view>);
 static_assert(is_trivially_copyable_v<wstring_view>);
 
+// Similar non-standard guarantees
+static_assert(is_trivially_move_constructible_v<string_view>);
+static_assert(is_trivially_copy_constructible_v<string_view>);
+static_assert(is_trivially_move_assignable_v<string_view>);
+static_assert(is_trivially_copy_assignable_v<string_view>);
+static_assert(is_trivially_destructible_v<string_view>);
+
+static_assert(is_trivially_move_constructible_v<wstring_view>);
+static_assert(is_trivially_copy_constructible_v<wstring_view>);
+static_assert(is_trivially_move_assignable_v<wstring_view>);
+static_assert(is_trivially_copy_assignable_v<wstring_view>);
+static_assert(is_trivially_destructible_v<wstring_view>);
+
 // noexcept assertions:
 // (functions that explicitly throw have their throws tested and therefore have no static_asserts)
 static_assert(noexcept(string_view{}), "default constructor not noexcept");