[Bug c++/107179] New: requires-expression gives hard error for inaccessible constructor

[Bug c++/107179] New: requires-expression gives hard error for inaccessible constructor

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107179

            Bug ID: 107179
           Summary: requires-expression gives hard error for inaccessible
                    constructor
           Product: gcc
           Version: 12.2.1
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

template<bool B> struct bool_constant { static constexpr bool value = B; };

template<typename T>
  struct is_implicitly_default_constructible
  : bool_constant<requires (void (*f)(const T&)) { f({}); }>
  { };

class X {
  X();
public:
  X(int);
};

static_assert( !is_implicitly_default_constructible<X>::value );


This should compile with -std=c++20 but doesn't:

conv.cc: In instantiation of 'struct is_implicitly_default_constructible<X>':
conv.cc:14:55:   required from here
conv.cc:5:53: error: 'X::X()' is private within this context
    5 |   : bool_constant<requires (void (*f)(const T&)) { f({}); }>
      |                                                    ~^~~~
conv.cc:9:3: note: declared private here
    9 |   X();
      |   ^
conv.cc:14:16: error: static assertion failed
   14 | static_assert( !is_implicitly_default_constructible<X>::value );
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Bug c++/107179] [11/12/13 Regression] requires-expression gives hard error for inaccessible constructor

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107179

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org
   Last reconfirmed|                            |2022-10-07
                 CC|                            |ppalka at gcc dot gnu.org
            Summary|requires-expression gives   |[11/12/13 Regression]
                   |hard error for inaccessible |requires-expression gives
                   |constructor                 |hard error for inaccessible
                   |                            |constructor
      Known to fail|                            |11.3.0, 12.2.0
     Ever confirmed|0                           |1
   Target Milestone|---                         |11.4
      Known to work|                            |10.3.0

--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Started with r11-6815-g79e1251b642db0

[Bug c++/107179] [11/12/13 Regression] requires-expression gives hard error for inaccessible constructor

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107179

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/107179] [11/12/13 Regression] requires-expression gives hard error for inaccessible constructor

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107179

--- 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:40c34beef620ed13c4113c893ed4335ccc1b8f92

commit r13-3641-g40c34beef620ed13c4113c893ed4335ccc1b8f92
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Nov 3 15:35:18 2022 -0400

    c++: requires-expr and access checking [PR107179]

    Like during satisfaction, we also need to avoid deferring access checks
    during substitution of a requires-expr because the outcome of an access
    check can determine the value of the requires-expr.  Otherwise (in
    deferred access checking contexts such as within a base-clause), the
    requires-expr may evaluate to the wrong result, and along the way a
    failed access check may leak out from it into a non-SFINAE context and
    cause a hard error (as in the below testcase).

            PR c++/107179

    gcc/cp/ChangeLog:

            * constraint.cc (tsubst_requires_expr): Make sure we're not
            deferring access checks.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-requires31.C: New test.

[Bug c++/107179] [11/12 Regression] requires-expression gives hard error for inaccessible constructor

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107179

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:668098c2e55c33f97e331c3160174bf12c3d88f7

commit r12-9227-g668098c2e55c33f97e331c3160174bf12c3d88f7
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Nov 3 15:35:18 2022 -0400

    c++: requires-expr and access checking [PR107179]

    Like during satisfaction, we also need to avoid deferring access checks
    during substitution of a requires-expr because the outcome of an access
    check can determine the value of the requires-expr.  Otherwise (in
    deferred access checking contexts such as within a base-clause), the
    requires-expr may evaluate to the wrong result, and along the way a
    failed access check may leak out from it into a non-SFINAE context and
    cause a hard error (as in the below testcase).

            PR c++/107179

    gcc/cp/ChangeLog:

            * constraint.cc (tsubst_requires_expr): Make sure we're not
            deferring access checks.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-requires31.C: New test.

    (cherry picked from commit 40c34beef620ed13c4113c893ed4335ccc1b8f92)

[Bug c++/107179] [11 Regression] requires-expression gives hard error for inaccessible constructor

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107179

--- Comment #4 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:c0658801e10d2e7e8b137e555d4c2817bf090ea9

commit r11-10802-gc0658801e10d2e7e8b137e555d4c2817bf090ea9
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Nov 3 15:35:18 2022 -0400

    c++: requires-expr and access checking [PR107179]

    Like during satisfaction, we also need to avoid deferring access checks
    during substitution of a requires-expr because the outcome of an access
    check can determine the value of the requires-expr.  Otherwise (in
    deferred access checking contexts such as within a base-clause), the
    requires-expr may evaluate to the wrong result, and along the way a
    failed access check may leak out from it into a non-SFINAE context and
    cause a hard error (as in the below testcase).

            PR c++/107179

    gcc/cp/ChangeLog:

            * constraint.cc (tsubst_requires_expr): Make sure we're not
            deferring access checks.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-requires31.C: New test.

    (cherry picked from commit 40c34beef620ed13c4113c893ed4335ccc1b8f92)

[Bug c++/107179] [11 Regression] requires-expression gives hard error for inaccessible constructor

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107179

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 11.4+