davidstone added inline comments.
================
Comment at: clang/test/CXX/class/class.init/class.copy.elision/p3.cpp:22
+ return c;
+}
+#else
----------------
Quuxplusone wrote:
> Quuxplusone wrote:
> > @rsmith @david_stone (or anyone), what is the status in C++20 of the
> > following test case?
> >
> > C&& test(C&& c) {
> > return c;
> > }
> >
> > I know we talked about this in person at CppCon 2018, and concluded that
> > our //intention// was for this to be legal, but that it wasn't actually
> > legal as-worded, because the returned thingie here is not an object but
> > rather a reference, and therefore none of
> > [P1825's](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1825r0.html)
> > wording actually covers it. Is that still the case? Is there an open issue
> > about this? Is there any appetite for Clang to just go ahead and //make//
> > this legal? (The current patch does //not// make this legal.)
> >
> > Relevant reading:
> > https://quuxplusone.github.io/blog/2018/09/25/perfect-backwarding/
> Apparently @davidstone has been active more recently than @david_stone... :)
Going through the wording in http://eel.is/c++draft/class.copy.elision#3
"An implicitly movable entity is a variable of automatic storage duration that
is either a non-volatile object or an rvalue reference to a non-volatile object
type."
So we are fine with a reference as the source. However, it then goes on to say
"...overload resolution to select the constructor for the copy or the
return_value overload to call is first performed as if the expression or
operand were an rvalue."
There is technically no constructor to call here, which I think means this
section does not apply.
I don't believe an issue has been raised for this yet, so I'll email CWG about
it.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D88220/new/
https://reviews.llvm.org/D88220
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