c++: sort candidates according to viability

This patch:

  * changes splice_viable to move the non-viable candidates to the end
    of the list instead of removing them outright
  * makes tourney move the best candidate to the front of the candidate
    list
  * adjusts print_z_candidates to preserve our behavior of printing only
    viable candidates when diagnosing ambiguity
  * adds a parameter to print_z_candidates to control this default behavior
    (the follow-up patch will want to print all candidates when diagnosing
    deletedness)

Thus after this patch we have access to the entire candidate list through
the best viable candidate.

This change also happens to fix diagnostics for the below testcase where
we currently neglect to note the third candidate, since the presence of
the two unordered non-strictly viable candidates causes splice_viable to
prematurely get rid of the non-viable third candidate.

gcc/cp/ChangeLog:

	* call.cc: Include "tristate.h".
	(splice_viable): Sort the candidate list according to viability.
	Don't remove non-viable candidates from the list.
	(print_z_candidates): Add defaulted only_viable_p parameter.
	By default only print non-viable candidates if there is no
	viable candidate.
	(tourney): Ignore non-viable candidates.  Move the true champ to
	the front of the candidates list, and update 'candidates' to
	point to the front.  Rename champ_compared_to_predecessor to
	previous_worse_champ.

gcc/testsuite/ChangeLog:

	* g++.dg/overload/error5.C: New test.

0 files changed, 0 insertions, 0 deletions