From 95198c5f2a2292b296f8abe78773f2bba3abd55f Mon Sep 17 00:00:00 2001
From: Ichthyostega <prg@ichthyostega.de>
Date: Fri, 15 Mar 2024 00:41:34 +0100
Subject: [PATCH] Library: need to exclude C++ stream sources from string
 conversion
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In the Lumiera code base, a convenient string conversion is used
an many places, and is also ''magically'' integrated into the usual
C++ style output with `<<` operators.

However, there is a ''gotcha'' — in the ''rare cases'' when we
actually want to use the C++ input/output framework to copy stream
data from an input source into an output sink, obviously we do not want
the input source to be »string converted«....
---
 src/lib/meta/trait.hpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/lib/meta/trait.hpp b/src/lib/meta/trait.hpp
index 0497d16ab..0b33c83cc 100644
--- a/src/lib/meta/trait.hpp
+++ b/src/lib/meta/trait.hpp
@@ -73,6 +73,8 @@ namespace std {
   template<class X> class reference_wrapper;
   template<class X> class shared_ptr;
   template<class X, class D> class unique_ptr;
+  template<class C, class T> class basic_filebuf;
+  template<class C> class char_traits;
 }
 namespace lib{
   template<class X, class B>  class P;
@@ -368,17 +370,23 @@ namespace meta {
             >
     { };
   
+  // need to exclude files and input streams from automatic string conversion
+  template<typename X>
+  struct is_StreamSource
+    : is_same<X, std::basic_filebuf<char, std::char_traits<char> > >
+    { };
+  
   /** when to use custom string conversions for output streams */
   template<typename X>
   struct use_StringConversion4Stream
     : __and_<is_class<typename Strip<X>::TypePlain>
             ,__not_<is_pointer<X>>
             ,__not_<can_lexical2string<X>>
+            ,__not_<is_StreamSource<X>>
             >
     { };
   
   
-  
   /** detect smart pointers */
   template<typename X>
   struct is_smart_ptr