implement changes

include/fmt/ranges.h

@@ -412,66 +412,61 @@ struct range_formatter<
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
     auto it = ctx.begin();
     auto end = ctx.end();
+    detail::maybe_set_debug_format(underlying_, true);
+    if (it == end) {
+      return underlying_.parse(ctx);
+    }
 
-    if (it != end && *it == 'n') {
+    switch (detail::to_ascii(*it)) {
+    case 'n':
       set_brackets({}, {});
       ++it;
-    } else {
-      bool check_for_s = false;
-      if (it != end && *it == '?') {
-        ++it;
-        detail::maybe_set_debug_format(underlying_, true);
-        set_brackets({}, {});
-        check_for_s = true;
-        is_debug = true;
-      }
-      if (it != end && *it == 's') {
-        if (!std::is_same<T, Char>::value) {
-          report_error("invalid format specifier");
-        }
-        if (!is_debug) {
-          set_brackets(detail::string_literal<Char, '"'>{},
-                       detail::string_literal<Char, '"'>{});
-        }
-        check_for_s = false;
-        is_string_format = true;
-        ++it;
-      }
-      if (check_for_s) {
+      break;
+    case '?':
+      is_debug = true;
+      set_brackets({}, {});
+      ++it;
+      FMT_FALLTHROUGH;
+    case 's':
+      if (it == end || *it != 's' || !std::is_same<T, Char>::value) {
         report_error("invalid format specifier");
       }
+      if (!is_debug) {
+        set_brackets(detail::string_literal<Char, '"'>{},
+                     detail::string_literal<Char, '"'>{});
+        set_separator({});
+        detail::maybe_set_debug_format(underlying_, false);
+      }
+      is_string_format = true;
+      ++it;
+      return it;
     }
 
     if (it != end && *it != '}') {
-      if (is_string_format || *it != ':')
-        report_error("invalid format specifier");
+      if (*it != ':') report_error("invalid format specifier");
+      detail::maybe_set_debug_format(underlying_, false);
       ++it;
-    } else {
-      if (!is_string_format) detail::maybe_set_debug_format(underlying_, true);
     }
 
     ctx.advance_to(it);
     return underlying_.parse(ctx);
   }
 
   template <typename Output, typename Iter, typename IterEnd, typename U = T,
-            enable_if_t<std::is_same<U, Char>::value, bool> = true>
+            FMT_ENABLE_IF(std::is_same<U, Char>::value)>
   auto write_debug_string(Output& out, Iter& it, IterEnd& end) const -> Output {
     auto buf = basic_memory_buffer<Char>();
     for (; it != end; ++it) {
-      auto&& item = *it;
-      buf.push_back(item);
+      buf.push_back(*it);
     }
-    format_specs spec_str{};
+    format_specs spec_str;
     spec_str.type = presentation_type::debug;
     return detail::write<Char>(
         out, basic_string_view<Char>(buf.data(), buf.size()), spec_str);
   }
   template <typename Output, typename Iter, typename IterEnd, typename U = T,
-            enable_if_t<!(std::is_same<U, Char>::value), bool> = true>
-  auto write_debug_string(Output& out, Iter& it, IterEnd& end) const -> Output {
-    detail::ignore_unused(it);
-    detail::ignore_unused(end);
+            FMT_ENABLE_IF(!std::is_same<U, Char>::value)>
+  auto write_debug_string(Output& out, Iter&, IterEnd&) const -> Output {
     return out;
   }
 
@@ -481,14 +476,14 @@ struct range_formatter<
     auto out = ctx.out();
     auto it = detail::range_begin(range);
     auto end = detail::range_end(range);
-    if (is_string_format && is_debug) {
+    if (is_debug) {
       return write_debug_string(out, it, end);
     }
 
     out = detail::copy<Char>(opening_bracket_, out);
     int i = 0;
     for (; it != end; ++it) {
-      if (i > 0 && !is_string_format) out = detail::copy<Char>(separator_, out);
+      if (i > 0) out = detail::copy<Char>(separator_, out);
       ctx.advance_to(out);
       auto&& item = *it;
       out = underlying_.format(mapper.map(item), ctx);