c++: Inhibit subsequent warnings/notes in diagnostic_groups with an inhibited warning [PR118163,PR118392]

Those 2 PRs show that even when using a *single* diagnostic_group, it's
possible to end up with a warning being inhibited and its associated
note still emitted, which leads to puzzling user experience. Example
from PR118392:

===
$ gcc/cc1plus inhibit-warn-3.C -w
inhibit-warn-3.C:10:17: note: only here as a ‘friend’
   10 |     friend void bar();
      |                 ^~~
===

Following a suggestion from ppalka@, this patch keeps track of the
"diagnostic depth" at which a warning in inhibited, and makes sure that
all subsequent notes at that depth or deeper are inhibited as well,
until a subsequent warning or error is accepted at that depth, or the
diagnostic_group or nesting level is popped.

	PR c++/118163
	PR c++/118392

gcc/ChangeLog:

	* diagnostic.cc (diagnostic_context::initialize): Initialize
	m_diagnostic_groups.m_inhibiting_notes_from.
	(diagnostic_context::inhibit_notes_in_group): New.
	(diagnostic_context::notes_inhibited_in_group): New
	(diagnostic_context::report_diagnostic): Call
	inhibit_notes_in_group and notes_inhibited_in_group.
	(diagnostic_context::end_group): Call inhibit_notes_in_group.
	(diagnostic_context::pop_nesting_level): Ditto.
	* diagnostic.h (diagnostic_context::m_diagnostic_groups): Add
	member to track the depth at which a warning has been inhibited.
	(diagnostic_context::notes_inhibited_in_group): Declare.
	(diagnostic_context::inhibit_notes_in_group): Declare.
	* doc/ux.texi: Document diagnostic_group behavior with regards
	to inhibited warnings.

gcc/testsuite/ChangeLog:

	* g++.dg/diagnostic/incomplete-type-2.C: New test.
	* g++.dg/diagnostic/incomplete-type-2a.C: New test.
	* g++.dg/diagnostic/inhibit-warn-3.C: New test.

0 files changed, 0 insertions, 0 deletions