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From: "m.cencora at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/103563] ostream operator<< resolved to variant containing
 type resulting in stack overflow
Date: Mon, 06 Dec 2021 16:09:20 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103563

m.cencora at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |m.cencora at gmail dot com

--- Comment #3 from m.cencora at gmail dot com ---
This is a known issue with operators in C++ in general.
That's why coding guidelines suggest that operators should be declared as
hidden friends (to prevent unexpected implicit conversions).

In your scenario you cannot make it a hidden friend, so constraint it with a
concept or
SFINAE:
https://godbolt.org/z/de869vW6h=