RFA (langhook): PATCH for c++/70029, ICE in verify_type with ref-qualifier

[Jason Merrill <jason at redhat dot com>]

The issue here is that the C++ front end represents the ref-qualifier
as a variant but includes it in the canonical type, because at the
language level the types are distinct.  Note that this is also true of
language-independent qualifiers like "const", so this doesn't seem
like an unreasonable thing for the front end to do.

But as a result, when build_type_attribute_qual_variant builds a
distinct type copy of the ref-qualified type, it is now its own main
variant, while the canonical type is still a variant of another type,
and verify_type doesn't like that.

This patch introduces a langhook to mimic for language-dependent
qualifiers the b_t_a_q_v behavior for cv-qualifiers, i.e. strip them
before making the copy and reintroduce them afterward.

Tested x86_64-pc-linux-gnu.  OK for trunk?

Attachment: 70029.diff
Description: Text document