coroutines: Do not promote temporaries that will be elided.

coroutines: Do not promote temporaries that will be elided.

We usually need to 'promote' (i.e. save to the coroutine frame) any temporary
variable that is in a target expression that must persist across an await
expression.  However, if the TE is just used as a direct initializer for
another object it will be elided - and we should not promote it since that
would lead to a DTOR call for something that is never constructed.

Since we now have a mechanism to tell if TEs will be elided, use that.

Although the PRs referenced initially appear to be different issues, they all
stem from this.

Co-Authored-By: Adrian Perl <adrian.perl@web.de>
Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
	PR c++/100611
	PR c++/101367
	PR c++/101976
	PR c++/99576

gcc/cp/ChangeLog:

	* coroutines.cc (find_interesting_subtree): Do not promote temporaries
	that are only used as direct initializers for some other object.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/pr100611.C: New test.
	* g++.dg/coroutines/pr101367.C: New test.
	* g++.dg/coroutines/pr101976.C: New test.
	* g++.dg/coroutines/pr99576_1.C: New test.
	* g++.dg/coroutines/pr99576_2.C: New test.