[Bug c++/104527] [11 Regression] ICE: tree check: accessed elt 1 of 'tree_vec' with 0 elts in hash, at cp/constraint.cc:2486

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104527

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:9cfb9378b93c01a4afff5b330bb4adf4904edf62

commit r11-10800-g9cfb9378b93c01a4afff5b330bb4adf4904edf62
Author: Patrick Palka <ppalka@redhat.com>
Date:   Sat Mar 12 15:00:40 2022 -0500

    c++: return-type-req in constraint using only outer tparms [PR104527]

    Here the template context for the atomic constraint has two levels of
    template parameters, but since it depends only on the innermost parameter
    T we use a single-level argument vector (built by get_mapped_args) during
    substitution into the atom.  We eventually pass this vector to
    do_auto_deduction as part of checking the return-type-requirement within
    the atom, but do_auto_deduction expects outer_targs to be a full set of
    arguments for sake of satisfaction.

    This patch fixes this by making get_mapped_args always return an
    argument vector whose depth corresponds to the template depth of the
    context in which the atomic constraint expression was written, instead
    of the highest parameter level that the expression happens to use.

            PR c++/104527

    gcc/cp/ChangeLog:

            * constraint.cc (normalize_atom): Set
            ATOMIC_CONSTR_EXPR_FROM_CONCEPT_P appropriately.
            (get_mapped_args):  Make static, adjust parameters.  Always
            return a vector whose depth corresponds to the template depth of
            the context of the atomic constraint expression.  Micro-optimize
            by passing false as exact to safe_grow_cleared and by collapsing
            a multi-level depth-one argument vector.
            (satisfy_atom): Adjust call to get_mapped_args and
            diagnose_atomic_constraint.
            (diagnose_atomic_constraint): Replace map parameter with an args
            parameter.
            * cp-tree.h (ATOMIC_CONSTR_EXPR_FROM_CONCEPT_P): Define.
            (get_mapped_args): Remove declaration.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-return-req4.C: New test.

    (cherry picked from commit 9413bb55185b9e88d84e91d5145d59f9f83b884a)