[Bug c++/112482] New: error when auto(x) is used in a variable initializer (block scope)

[Bug c++/112482] New: error when auto(x) is used in a variable initializer (block scope)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112482

            Bug ID: 112482
           Summary: error when auto(x) is used in a variable initializer
                    (block scope)
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

Discovered while working on bug 112410.  It's very similar, but the underlying
issue is different.

// { dg-do compile { target c++23 } }

struct A {
   A(int,int);
};

void
g (int a)
{
  A b2(auto(a), 42);
}

$ xg++ -c auto-fncast15.C -std=c++23
auto-fncast15.C: In function ‘void g(int)’:
auto-fncast15.C:10:8: error: ‘auto’ parameter not permitted in this context
   10 |   A b2(auto(a), 42);
      |        ^~~~

[Bug c++/112482] error when auto(x) is used in a variable initializer (block scope)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112482

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-11-11

[Bug c++/112482] error when auto(x) is used in a variable initializer (block scope)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112482

--- Comment #1 from GCC 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:1ae71269890f532a2bb06b84fc49f474c16e230d

commit r14-6563-g1ae71269890f532a2bb06b84fc49f474c16e230d
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Dec 14 12:01:21 2023 -0500

    c++: fix parsing with auto(x) at block scope [PR112482]

    This is sort of like r14-5514, but at block scope.  Consider

      struct A { A(int, int); };
      void
      g (int a)
      {
        A bar(auto(a), 42); // not a fn decl
      }

    where we emit error: 'auto' parameter not permitted in this context
    which is bogus -- bar doesn't declare a function, so the auto is OK,
    but we don't know it till we've seen the second argument.  The error
    comes from grokdeclarator invoked just after we've parsed the auto(a).

    A possible approach seems to be to delay the auto parameter checking
    and only check once we know we are indeed dealing with a function
    declaration.  For tparms, we should still emit the error right away.

            PR c++/112482

    gcc/cp/ChangeLog:

            * decl.cc (grokdeclarator): Do not issue the auto parameter error
while
            tentatively parsing a function parameter.
            * parser.cc (cp_parser_parameter_declaration_clause): Check it
here.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp23/auto-fncast15.C: New test.

[Bug c++/112482] error when auto(x) is used in a variable initializer (block scope)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112482

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed for GCC 14.