https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96531
--- Comment #2 from CVS Commits ---
The master branch has been updated by Patrick Palka :
https://gcc.gnu.org/g:e5d72c840a226fdbab65912f97d42a1dbdaf6ed2
commit r11-3296-ge5d72c840a226fdbab65912f97d42a1dbdaf6ed2
Author: Patrick Palka
Date: Sat Sep 19 11:02:46 2020 -0400
c++: Fix self-mapping in map_arguments [PR96531, PR97103]
With r10-8077 we stopped passing the argified current_template_parms to
normalize_constraint_expression from finish_nested_requirement, and
instead made map_arguments perform a self-mapping of parameters when
args is NULL. But we're currently not handling parameter packs and
BOUND_TEMPLATE_TEMPLATE_PARMs properly during this self-mapping, which
leads to ICEs later during satisfaction.
To properly handle self-mapping of a parameter pack, this patch
extends template_parm_to_arg to handle TEMPLATE_PARM_P nodes, and
makes map_arguments use it. (This change revealed that the call to
template_parm_to_arg in convert_generic_types_to_packs was a no-op
because the argument 't' is never a TREE_LIST, so this patch
additionally removes this call.)
As for bound ttps, map_arguments before r10-8077 would map a
BOUND_TEMPLATE_TEMPLATE_PARM not to itself but to its underlying
TEMPLATE_TEMPLATE_PARM. We could restore this behavior in
map_arguments, but since a bound ttp is not really a template parameter
it seems better to make keep_template_parm not give us a bound ttp in
the first place. So this patch makes keep_template_parm return the
underlying ttp when it sees a bound ttp.
gcc/cp/ChangeLog:
PR c++/96531
PR c++/97103
* constraint.cc (map_arguments): Call template_parm_to_arg
in the self-mapping case.
(finish_shorthand_constraint): No need to build a TREE_LIST
before calling template_parm_to_arg.
* pt.c (template_parm_to_arg): Rewrite to handle TEMPLATE_PARM_P
nodes as well as DECL_TEMPLATE_PARM_P nodes, and to make the
overlying TREE_LIST node optional.
(keep_template_parm): Don't record a BOUND_TEMPLATE_TEMPLATE_PARM,
instead record its corresponding TEMPLATE_TEMPLATE_PARM.
(convert_generic_types_to_packs): Don't call
template_parm_to_arg.
gcc/testsuite/ChangeLog:
PR c++/96531
PR c++/97103
* g++.dg/cpp2a/concepts-ttp2.C: New test.
* g++.dg/cpp2a/concepts-variadic1.C: New test.
