From b2be6dbbef3b5b62ecbfc82164f740cbc4ca568f Mon Sep 17 00:00:00 2001
From: Sebastien Loriot <sloriot.ml@gmail.com>
Date: Fri, 18 Aug 2023 09:25:39 +0200
Subject: [PATCH] fix istream for optional

Co-authored-by: Laurent Rineau <Laurent.Rineau@cgal.org>
---
 Stream_support/include/CGAL/IO/io.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Stream_support/include/CGAL/IO/io.h b/Stream_support/include/CGAL/IO/io.h
index e57d4327bac6..d9c2ea7f761a 100644
--- a/Stream_support/include/CGAL/IO/io.h
+++ b/Stream_support/include/CGAL/IO/io.h
@@ -281,7 +281,11 @@ class Input_rep<std::optional<T>>
   Input_rep( std::optional<T>& tt) : t(tt) {}
 
   //! perform the input, calls \c operator\>\> by default.
-  std::istream& operator()( std::istream& is) const { return (is >> t.value()); }
+  std::istream& operator()( std::istream& is) const {
+    T v;
+    if(is >> v) t = v;
+    return is;
+  }
 };
 
 #if CGAL_FORCE_IFORMAT_DOUBLE || \