[Bug c++/83167] decltype((x)) inside lambda is considered odr-use if x is not a reference

[Bug c++/83167] decltype((x)) inside lambda is considered odr-use if x is not a reference

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83167

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=79620,
                   |                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=94376

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
No compiler fully accepts this code.
clang fails on the 2nd and 4th asserts
ICC fails on the 2nd assert only
MSVC fails on all 4 asserts.
GCC fails on the first 2 asserts.

GCC is the only one that fails on the 1st assert via not being captured.

[Bug c++/83167] decltype((x)) inside lambda is considered odr-use if x is not a reference

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83167

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I might have seen a dup of this bug before.

[Bug c++/83167] decltype((x)) inside lambda is considered odr-use if x is not a reference

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83167

--- Comment #3 from GCC 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:d9965fef40794d548021d2e34844e5fafeca4ce5

commit r14-6350-gd9965fef40794d548021d2e34844e5fafeca4ce5
Author: Patrick Palka <ppalka@redhat.com>
Date:   Fri Dec 8 16:57:13 2023 -0500

    c++: decltype of (non-captured variable) [PR83167]

    For decltype((x)) within a lambda where x is not captured, we dubiously
    require that the lambda has a capture default, unlike for decltype(x).
    But according to [expr.prim.id.unqual]/3 we should just ignore the lambda
    in this case.  This patch narrowly fixes this issue by disabling the
    capture_decltype handling and falling back to the ordinary handling when
    the innermost lambda has no capture-default.  In fact, we can restrict
    the special handling to only by-copy lambdas since that's what
    [expr.prim.id.unqual]/3 is concerned with; for by-ref implicit captures
    both code paths should give the same result anyway.

    During review some other issues were discovered which are documented in
    a new FIXME.

            PR c++/83167

    gcc/cp/ChangeLog:

            * semantics.cc (capture_decltype): Inline into its only caller ...
            (finish_decltype_type): ... here.  Update nearby comment to refer
            to recent standard.  Add FIXME.  Restrict uncaptured variable type
            transformation to happen only for lambdas with a by-copy
            capture-default.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp0x/lambda/lambda-decltype4.C: New test.

[Bug c++/83167] decltype((x)) inside lambda is considered odr-use if x is not a reference

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83167

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.0
                 CC|                            |ppalka at gcc dot gnu.org
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Narrowly fixed for GCC 14, thanks for the bug report.