[Bug c++/110565] New: Incomplete note on why initializing int& with int is ill-formed

[Bug c++/110565] New: Incomplete note on why initializing int& with int is ill-formed

[blubban at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110565

            Bug ID: 110565
           Summary: Incomplete note on why initializing int& with int is
                    ill-formed
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: blubban at gmail dot com
  Target Milestone: ---

struct X {
    X(int&);
    X(X&&) = delete; // the issue reproduces without this line, but the error
is clearer with it
};

template<int>
void f() {
    new X(0);
}


Expected output:

<source>: In function 'void f()':
<source>:8:12: error: no matching function for call to 'X::X(int)'
    8 |     new X(0);
      |            ^
<source>:2:5: note: candidate: 'X::X(int&)' (near match)
    2 |     X(int&);
      |     ^
<source>:2:5: note:   conversion of argument 1 would be ill-formed:
<source>:8:11: error: cannot bind non-const lvalue reference of type 'int&' to
an rvalue of type 'int'


Actual output:

<source>: In function 'void f()':
<source>:8:12: error: no matching function for call to 'X::X(int)'
    8 |     new X(0);
      |            ^
<source>:2:5: note: candidate: 'X::X(int&)' (near match)
    2 |     X(int&);
      |     ^
<source>:2:5: note:   conversion of argument 1 would be ill-formed:


The template and new-expression are necessary; the error is proper without
them.

https://godbolt.org/z/c1Er5nsjd

[Bug c++/110565] [10/11/12/13/14 Regression] Incomplete note on why initializing int& with int is ill-formed

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110565

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Incomplete note on why      |[10/11/12/13/14 Regression]
                   |initializing int& with int  |Incomplete note on why
                   |is ill-formed               |initializing int& with int
                   |                            |is ill-formed
     Ever confirmed|0                           |1
      Known to fail|                            |5.1.0
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-07-05
      Known to work|                            |4.9.4

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC 4.9 and before gave a slightly better error message:
<source>: In function 'void f()':
<source>:8:12: error: no matching function for call to 'X::X(int)'
     new X(0);
            ^
<source>:8:12: note: candidate is:
<source>:2:5: note: X::X(int&)
     X(int&);
     ^
<source>:2:5: note:   no known conversion for argument 1 from 'int' to 'int&'

[Bug c++/110565] [10/11/12/13/14 Regression] Incomplete note on why initializing int& with int is ill-formed

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110565

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |13.1.1
   Target Milestone|---                         |10.5

[Bug c++/110565] [11/12/13/14 Regression] Incomplete note on why initializing int& with int is ill-formed

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110565

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.

[Bug c++/110565] [11/12/13/14 Regression] Incomplete note on why initializing int& with int is ill-formed

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110565

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |law at gcc dot gnu.org
           Priority|P3                          |P2

[Bug c++/110565] [11/12/13/14 Regression] Incomplete note on why initializing int& with int is ill-formed

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110565

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The diagnostic was changed by r5-601-gd02f620dc0bb3b

Author: Jason Merrill
Date:   Wed May 14 17:48:07 2014

    re PR c++/20332 (poor diagnostic when bind non lvalue to a reference for
default arguments)

            PR c++/20332
            PR c++/21631
            * call.c (reference_binding): Treat lvalue/rvalue mismatch and
            dropped cv-quals as a bad conversion.
            (convert_like_real) [ck_ref_bind]: Explain them.
            (compare_ics): Check badness before stripping reference
            bindings.  Handle comparing bad reference bindings.
            * typeck.c (comp_cv_qualification): Add overload that just takes
            integers.
            * cp-tree.h: Declare it.