LWG3551 borrowed_{iterator,subrange}_t are overspecified

Author: jensmaurer

source/ranges.tex

@@ -134,11 +134,10 @@
   struct dangling;
 
   template<@\libconcept{range}@ R>
-    using borrowed_iterator_t = conditional_t<@\libconcept{borrowed_range}@<R>, iterator_t<R>, dangling>;
+    using borrowed_iterator_t = @\seebelow@;
 
   template<@\libconcept{range}@ R>
-    using borrowed_subrange_t =
-      conditional_t<@\libconcept{borrowed_range}@<R>, subrange<iterator_t<R>>, dangling>;
+    using borrowed_subrange_t = @\seebelow@;
 
   // \ref{range.empty}, empty view
   template<class T>
@@ -1884,6 +1883,19 @@
 model \libconcept{borrowed_range}.
 \end{example}
 
+\pnum
+For a type \tcode{R} that models \libconcept{range}:
+\begin{itemize}
+\item
+if \tcode{R} models \libconcept{borrowed_range}, then
+\tcode{borrowed_iterator_t<R>} denotes \tcode{iterator_t<R>}, and
+\tcode{borrowed_subrange_t<R>} denotes \tcode{subrange<iterator_t<R>>};
+\item
+otherwise,
+both \tcode{borrowed_iterator_t<R>} and \tcode{borrowed_subrange_t<R>}
+denote \tcode{dangling}.
+\end{itemize}
+
 \rSec1[range.factories]{Range factories}
 
 \rSec2[range.factories.general]{General}