c++: ICE w/ ambig and non-strictly-viable cands [PR115239]
Here during overload resolution we have two strictly viable ambiguous
candidates #1 and #2, and two non-strictly viable candidates #3 and #4
which we hold on to ever since r14-6522. These latter candidates have
an empty second arg conversion since the first arg conversion was deemed
bad, and this trips up joust when called on #3 and #4 which assumes all
arg conversions are there.
We can fix this by making joust robust to empty arg conversions, but in
this situation we shouldn't need to compare #3 and #4 at all given that
we have a strictly viable candidate. To that end, this patch makes
tourney shortcut considering non-strictly viable candidates upon
encountering ambiguity between two strictly viable candidates (taking
advantage of the fact that the candidates list is sorted according to
viability via splice_viable).
PR c++/115239
gcc/cp/ChangeLog:
* call.cc (tourney): Don't consider a non-strictly viable
candidate as the champ if there was ambiguity between two
strictly viable candidates.
gcc/testsuite/ChangeLog:
* g++.dg/overload/error7.C: New test.
Reviewed-by: Jason Merrill <jason@redhat.com>
(cherry picked from commit
7fed7e9bbc57d502e141e079a6be2706bdbd4560)