Fix a regression in named argument handling introduced by prepare

include/fmt/format.h

@@ -1806,11 +1806,9 @@ struct string_view_metadata {
       : offset_(view.data() - primary_string.data()), size_(view.size()) {}
   FMT_CONSTEXPR string_view_metadata(std::size_t offset, std::size_t size)
       : offset_(offset), size_(size) {}
-  template <typename S, typename Char = enable_if_t<
-                            internal::is_string<S>::value, char_t<S>>>
-  FMT_CONSTEXPR basic_string_view<Char> to_view(S&& str) const {
-    const auto view = to_string_view(str);
-    return basic_string_view<Char>(view.data() + offset_, size_);
+  template <typename Char>
+  FMT_CONSTEXPR basic_string_view<Char> to_view(const Char* str) const {
+    return {str + offset_, size_};
   }
 
   std::size_t offset_;

include/fmt/prepare.h

@@ -262,7 +262,7 @@ class prepared_format {
 
       switch (part.which) {
       case format_part_t::which_value::text: {
-        const auto text = value.text.to_view(format_view);
+        const auto text = value.text.to_view(format_view.data());
         auto output = ctx.out();
         auto&& it = internal::reserve(output, text.size());
         it = std::copy_n(text.begin(), text.size(), it);
@@ -276,16 +276,17 @@ class prepared_format {
 
       case format_part_t::which_value::named_argument_id: {
         advance_parse_context_to_specification(parse_ctx, part);
-        const auto named_arg_id = value.named_arg_id.to_view(format_view);
+        const auto named_arg_id =
+            value.named_arg_id.to_view(format_view.data());
         format_arg<Range>(parse_ctx, ctx, named_arg_id);
       } break;
       case format_part_t::which_value::specification: {
         const auto& arg_id_value = value.spec.arg_id.val;
-        const auto arg =
-            value.spec.arg_id.which ==
-                    format_part_t::argument_id::which_arg_id::index
-                ? ctx.arg(arg_id_value.index)
-                : ctx.arg(arg_id_value.named_index.to_view(format_));
+        const auto arg = value.spec.arg_id.which ==
+                                 format_part_t::argument_id::which_arg_id::index
+                             ? ctx.arg(arg_id_value.index)
+                             : ctx.arg(arg_id_value.named_index.to_view(
+                                   to_string_view(format_).data()));
 
         auto specs = value.spec.parsed_specs;