[Bug libstdc++/52114] SFINAE out the rvalue iostream operators to give better error messages

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52114

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-02-04 21:44:24 UTC ---
(In reply to comment #3)
> (PS: Daniel tweaked tuple_cat the same way)

There is a difference here: For tuple_cat we have a user constraint that says
that the template argument shall be a tuple_cat, but encourage the library to
support other types satisfying the tuple-like protocol. Further, tuple_cat is a
named function and hard to reach unintentionally. I tend to say that the
approach here is what a good library should do. But it might be a good idea to
open a library issue to require a reduced set of overload resolution
participation for any conforming implementation for the new two generic
inserter and extractor.