https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100476
--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> --- (In reply to Jason Merrill from comment #2) > (In reply to Iain Sandoe from comment #1) > > I am by no means an expert at reading standardese - and it might be that I'm > > not alone, (library writers might have made the same assumption) but it > > seems to me that: > > > > http://eel.is/c++draft/dcl.fct.def.coroutine#7 > > > > Doe not make any specification about what get_return_object() returns, > > only that it is possible to use it either (a) to initialise the return value > > directly or (b) to construct a return value object from it. > > It says that you initialize the return value from get_return_object(), which > sounds like > > return promise.get_return_object(); > > in a non-coroutine, which is an error if get_return_object returns void. In general, you can't construct an object from a void expression; a void expression can't be used as an operand for anything. struct A { }; A a1 = A(); // default-initialize A a2 = A((void)0); // error
