[Bug c++/96229] Invalid specialization accepted when also constrained in base template template parameter

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96229

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:6b1b5c255f859e75a2d74ae58a011e846d87a277

commit r11-3713-g6b1b5c255f859e75a2d74ae58a011e846d87a277
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Oct 8 00:05:36 2020 -0400

    c++: Set the constraints of a class type sooner [PR96229]

    In the testcase below, during processing (at parse time) of Y's base
    class X<Y>, convert_template_argument calls is_compatible_template_arg
    to check if the template argument Y is no more constrained than the
    parameter P.  But at this point we haven't yet set Y's constraints, so
    get_normalized_constraints_from_decl yields NULL_TREE as the normal form
    and caches this result into the normalized_map.

    We set Y's constraints later in cp_parser_class_specifier_1 but the
    stale normal form in the normalized_map remains.  This ultimately causes
    us to miss the constraint failure for Y<Z> because according to the
    cached normal form, Y is not constrained.

    This patch fixes this issue by moving up the call to
    associate_classtype_constraints so that we set constraints before we
    start processing a class's bases.

    gcc/cp/ChangeLog:

            PR c++/96229
            * parser.c (cp_parser_class_specifier_1): Move call to
            associate_classtype_constraints from here to ...
            (cp_parser_class_head): ... here.
            * pt.c (is_compatible_template_arg): Correct documentation to
            say "argument is _no_ more constrained than the parameter".

    gcc/testsuite/ChangeLog:

            PR c++/96229
            * g++.dg/cpp2a/concepts-class2.C: New test.