c++: Fix SFINAE for deleted explicit specializations [PR119343]

When checking a deleted explicit specialization in a SFINAE context,
we were incorrectly selecting a partial specialization because
resolve_nondeduced_context was calling mark_used.  But resolving an
overload to a single function (per DR 115) does not constitute ODR-use,
so mark_used shouldn't be called there.  Instead callers should call
mark_used or mark_single_function on the result to uniformly handle all
resolvable overloads (even non-template-id ones).

This turns out to fix the below testcase because it causes convert_to_void
for void(X::template g<0>) to properly propagate ODR-use failure (due to
deleted g<0>) and return error_mark_node instead of returning void_node.

	PR c++/119343

gcc/cp/ChangeLog:

	* pt.cc (resolve_nondeduced_context): Remove mark_used call.

gcc/testsuite/ChangeLog:

	* g++.dg/template/sfinae-deleted-pr119343.C: New test.

Signed-off-by: Egas Ribeiro <egas.g.ribeiro@tecnico.ulisboa.pt>
Reviewed-by: Patrick Palka <ppalka@redhat.com>

0 files changed, 0 insertions, 0 deletions