c++: ambiguous member lookup for rewritten cands [PR113529]
Here we handle the operator expression u < v inconsistently: in a SFINAE
context we accept it, and in a non-SFINAE context we reject it with
error: request for member 'operator<=>' is ambiguous
as per [class.member.lookup]/6. This inconsistency is ultimately
because we neglect to propagate error_mark_node after recursing in
add_operator_candidates, fixed like so.
PR c++/113529
gcc/cp/ChangeLog:
* call.cc (add_operator_candidates): Propagate error_mark_node
result after recursing to find rewritten candidates.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/spaceship-sfinae3.C: New test.
Reviewed-by: Jason Merrill <jason@redhat.com>
(cherry picked from commit
fecb45a936d62ca24dd8b4985ea0555c28edefa8)