Quuxplusone added a comment.
@sberg: Thanks for the example! @mizvekov's comments are correct, but I wanted
to put some more comments here for posterity. (I'll also try to find a place
for this real-world example in the next revision of p2266
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2266r1.html>.)
The code in question is `o3tl::temporary`, documented as "Cast an rvalue to an
lvalue." and implemented as `template<class T> T& temporary(T&& x) { return x;
}`
https://docs.libreoffice.org/o3tl/html/temporary_8hxx_source.html
p2266 proposes to break this code in C++23, by making the expression `x` an
xvalue. EWG was well aware that p2266 would break this exact kind of
"laundering" function, which takes an rvalue and launders it into an lvalue
without a cast. This breakage was generally (though I'm sure not universally)
seen as a good thing. We weren't aware of any specific real-world examples of
such "laundering" functions, though, so this is very useful info.
As Matheus says, the best way to fix the code is to add an explicit cast:
`return static_cast<T&>(x);`.
Repository:
rG LLVM Github Monorepo
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https://reviews.llvm.org/D99005/new/
https://reviews.llvm.org/D99005
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