[Bug c++/107276] ICE Deducing return type from ill-formed structured binding name since r13-2905-g772d532e0ba1e4b2

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:f7d8ccfda2d5c90dac97b1a3ede8b10391a3cc40

commit r13-3462-gf7d8ccfda2d5c90dac97b1a3ede8b10391a3cc40
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Oct 20 15:55:28 2022 -0400

    c++: ICE with invalid structured bindings [PR107276]

    This test ICEs in C++23 because we reach the new code in do_auto_deduction:

    30468   if (cxx_dialect >= cxx23
    30469       && context == adc_return_type
    30470       && (!AUTO_IS_DECLTYPE (auto_node)
    30471           || !unparenthesized_id_or_class_member_access_p (init))
    30472       && (r = treat_lvalue_as_rvalue_p (maybe_undo_parenthesized_ref
(init),
    30473                                         /*return*/true)))

    where 'init' is "VIEW_CONVERT_EXPR<<<< error >>>>(y)", and then the move
    in treat_lvalue_as_rvalue_p returns error_mark_node whereupon
    set_implicit_rvalue_p crashes.

    I don't think such V_C_Es are useful so let's not create them.  But that
    won't fix the ICE so I'm checking the return value of move.  A structured
    bindings decl can have an error type, that is set in cp_finish_decomp:

     8908           TREE_TYPE (first) = error_mark_node;

    therefore I think treat_lvalue_as_rvalue_p just needs to cope.

            PR c++/107276

    gcc/cp/ChangeLog:

            * typeck.cc (treat_lvalue_as_rvalue_p): Check the return value of
move.

    gcc/ChangeLog:

            * tree.cc (maybe_wrap_with_location): Don't create a location
wrapper
            when the type is erroneous.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/decomp4.C: New test.