libstdc++: Do not use CTAD for _Utf32_view alias template

We were relying on P1814R0 (CTAD for alias templates) which isn't
supported by Clang. We can just not use CTAD and provide an explicit
template argument list for _Utf32_view.

Ideally we'd define a deduction guide for _Grapheme_cluster_view that
uses views::all_t to properly convert non-views to views, but all_t is
defined in <ranges> and we don't want to include all of that in
<bits/unicode.h>. So just make it require a view for now, which can be
cheaply copied.

Although it's not needed yet, it would also be more correct to
specialize enable_borrowed_range for the views in <bits/unicode.h>.

libstdc++-v3/ChangeLog:

	* include/bits/unicode.h (_Grapheme_cluster_view): Require view.
	Do not use CTAD for _Utf32_view.
	(__format_width, __truncate): Do not use CTAD.
	(enable_borrowed_range<_Utf_view<T, R>>): Define specialization.
	(enable_borrowed_range<_Grapheme_cluster_view<R>>): Likewise.

diff --git a/libstdc++-v3/include/bits/unicode.h b/libstdc++-v3/include/bits/unicode.h
index f1b2b359bdf8889e5aae2a646b79f920df33d04c..d35c83d009059bcd37493dae0bf627fb88cec1f9 100644 (file)
--- a/libstdc++-v3/include/bits/unicode.h
+++ b/libstdc++-v3/include/bits/unicode.h
@@ -714,15 +714,15 @@ inline namespace __v15_1_0
   };
 
   // Split a range into extended grapheme clusters.
-  template<ranges::forward_range _View>
+  template<ranges::forward_range _View> requires ranges::view<_View>
     class _Grapheme_cluster_view
     : public ranges::view_interface<_Grapheme_cluster_view<_View>>
     {
     public:
 
       constexpr
-      _Grapheme_cluster_view(const _View& __v)
-      : _M_begin(_Utf32_view(__v).begin())
+      _Grapheme_cluster_view(_View __v)
+      : _M_begin(_Utf32_view<_View>(std::move(__v)).begin())
       { }
 
       constexpr auto begin() const { return _M_begin; }
@@ -946,7 +946,7 @@ inline namespace __v15_1_0
     {
       if (__s.empty()) [[unlikely]]
        return 0;
-      _Grapheme_cluster_view __gc(__s);
+      _Grapheme_cluster_view<basic_string_view<_CharT>> __gc(__s);
       auto __it = __gc.begin();
       const auto __end = __gc.end();
       size_t __n = __it.width();
@@ -964,7 +964,7 @@ inline namespace __v15_1_0
       if (__s.empty()) [[unlikely]]
        return 0;
 
-      _Grapheme_cluster_view __gc(__s);
+      _Grapheme_cluster_view<basic_string_view<_CharT>> __gc(__s);
       auto __it = __gc.begin();
       const auto __end = __gc.end();
       size_t __n = __it.width();
@@ -1058,6 +1058,19 @@ inline namespace __v15_1_0
 
 } // namespace __unicode
 
+namespace ranges
+{
+  template<typename _To, typename _Range>
+    inline constexpr bool
+    enable_borrowed_range<std::__unicode::_Utf_view<_To, _Range>>
+      = enable_borrowed_range<_Range>;
+
+  template<typename _Range>
+    inline constexpr bool
+    enable_borrowed_range<std::__unicode::_Grapheme_cluster_view<_Range>>
+      = enable_borrowed_range<_Range>;
+} // namespace ranges
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // C++20