[Bug c++/98767] New: Function signature lost in concept diagnostic message

[Bug c++/98767] New: Function signature lost in concept diagnostic message

[antoshkka at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98767

            Bug ID: 98767
           Summary: Function signature lost in concept diagnostic message
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antoshkka at gmail dot com
  Target Milestone: ---

Consider the example:


template <typename Function, typename T>
concept Callable1Arg = requires(Function func, T value) {
    func(value);
};

// Should fail and fails:
static_assert(Callable1Arg<int(*)(int*), bool>);


The diagnotics has the following line:
"in requirements with 'Function func', 'T value' [with T = bool; Function = int
(*)()]"

However the type of the Function is "int (*)(int*)" not "int (*)()"


Godbolt playground: https://godbolt.org/z/afKqq5

[Bug c++/98767] Function signature lost in concept diagnostic message

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98767

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-01-20
     Ever confirmed|0                           |1

[Bug c++/98767] Function signature lost in concept diagnostic message

[ensadc at mailnesia dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98767

ensadc at mailnesia dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ensadc at mailnesia dot com

--- Comment #1 from ensadc at mailnesia dot com ---
The parameter list is printed by `pp_cxx_parameter_declaration_clause` defined
in gcc/cp/cxx-pretty-print.c
(https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/cp/cxx-pretty-print.c;h=a22eea5239c33ed946abe46539e588b04e7beca7;hb=HEAD#l1538
), where the parameter types are printed in a loop that starts with:

>    for (; args; args = TREE_CHAIN (args), types = TREE_CHAIN (types))

Here `args` was initialized with:

>       args = type_p ? NULL : FUNCTION_FIRST_USER_PARM (t);

It seems that when a type is passed to `pp_cxx_parameter_declaration_clause`,
`args` is always set to NULL, and the loop is never entered.

[Bug c++/98767] Function signature lost in concept diagnostic message

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98767

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |ppalka at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org

[Bug c++/98767] Function signature lost in concept diagnostic message

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98767

--- 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:87fc34a461cf362947a430d8a241f653fd83bc7b

commit r12-86-g87fc34a461cf362947a430d8a241f653fd83bc7b
Author: Patrick Palka <ppalka@redhat.com>
Date:   Fri Apr 23 08:47:02 2021 -0400

    c++: Fix pretty printing pointer to function type [PR98767]

    When pretty printing a pointer to function type,
    pp_cxx_parameter_declaration_clause ends up always outputting an empty
    function parameter list because the loop that outputs the list iterates
    over 'args' instead of 'types', and 'args' is empty when a FUNCTION_TYPE
    is passed to this routine (as opposed to a FUNCTION_DECL).

    This patch fixes this by making the loop iterate over 'types' instead.
    This patch also moves the retrofitted chain-of-PARM_DECLs printing from
    here to pp_cxx_requires_expr, the only caller that uses it.  Doing so
    lets us easily output the trailing '...' in the parameter list of a
    variadic function, which this patch also implements.

    gcc/cp/ChangeLog:

            PR c++/98767
            * cxx-pretty-print.c (pp_cxx_parameter_declaration_clause):
            Adjust parameter list loop to iterate over 'types' instead of
            'args'.  Output the trailing '...' for a variadic function.
            Remove PARM_DECL support.
            (pp_cxx_requires_expr): Pretty print the parameter list directly
            instead of going through pp_cxx_parameter_declaration_clause.

    gcc/testsuite/ChangeLog:

            PR c++/98767
            * g++.dg/concepts/diagnostic17.C: New test.

[Bug c++/98767] Function signature lost in concept diagnostic message

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98767

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Closing as fixed for GCC 12