LWG4082 views::concat(r) is well-formed when r is an output_range

Author: burblebee

source/ranges.tex

@@ -8474,7 +8474,8 @@
 Given a pack of subexpressions \tcode{Es...},
 the expression \tcode{views::concat(Es...)} is expression-equivalent to
 \begin{itemize}
-\item \tcode{views::all(Es...)} if \tcode{Es} is a pack with only one element,
+\item \tcode{views::all(Es...)} if \tcode{Es} is a pack with only one element
+whose type models \libconcept{input_range},
 \item otherwise, \tcode{concat_view(Es...)}.
 \end{itemize}
 \begin{example}