[Bug c++/53822] New: Diagnostic: spell out type in ambiguous call

[Bug c++/53822] New: Diagnostic: spell out type in ambiguous call

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

             Bug #: 53822
           Summary: Diagnostic: spell out type in ambiguous call
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: glisse@gcc.gnu.org


Hello,

void f(float);
void f(double);
int main(){
  typedef unsigned NT;
  NT i=3;
  f(i);
}

mp.cc: In function ‘int main()’:
mp.cc:6:6: error: call of overloaded ‘f(NT&)’ is ambiguous
mp.cc:6:6: note: candidates are:
mp.cc:1:6: note: void f(float)
mp.cc:2:6: note: void f(double)

Notice that the error message never mentions "unsigned". In the middle of some
deep templated code, finding out what the problematic NT is can be hard.

[Bug c++/53822] Diagnostic: spell out type in ambiguous call

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> 2012-06-30 16:59:13 UTC ---
Hmm, the true message from 4.8, not 4.7 this time:

mp.cc: In function 'int main()':
mp.cc:6:6: error: call of overloaded 'f(NT&)' is ambiguous
   f(i);
      ^
mp.cc:6:6: note: candidates are:
mp.cc:1:6: note: void f(float)
 void f(float);
      ^
mp.cc:2:6: note: void f(double)
 void f(double);
      ^

[Bug c++/53822] Diagnostic: spell out type in ambiguous call

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-04-19 15:27:28 UTC ---
Makes sense to me and must be pretty easy to implement.

[Bug c++/53822] spell out typedefs in ambiguous call

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> ---
Created attachment 31564
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31564&action=edit
patch

(mostly untested)

This changes the message to:
error: call of overloaded 'f(NT&)' {aka 'f(unsigned int&)'} is ambiguous

As far as I can tell, "%#A" is unused, so it seems ok to hijack it.

It isn't very nice because without typedefs it will repeat the same thing
twice, but printing [with NT=unsigned int] seems more complicated to me.

Then maybe the example is not that well chosen, because in the more interesting
cases NT depends on template parameters, and that may make [with ...] easier to
implement (or not).

[Bug c++/53822] spell out typedefs in ambiguous call

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

--- Comment #5 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #4)
> Created attachment 31564 [details]
> patch
> 
> (mostly untested)
> 
> This changes the message to:
> error: call of overloaded 'f(NT&)' {aka 'f(unsigned int&)'} is ambiguous
> 
> As far as I can tell, "%#A" is unused, so it seems ok to hijack it.
> 
> It isn't very nice because without typedefs it will repeat the same thing
> twice, but printing [with NT=unsigned int] seems more complicated to me.

There is code in error.c:type_to_string to print "{aka ". It does some tricks
to avoid printing aka when there are no typedefs. Perhaps args_to_string()
should call type_to_string() instead of calling dump_type directly. With that,
it prints:


test.cc:6:6: error: call of overloaded ‘f(NT& {aka unsigned int&})’ is
ambiguous

I am not sure if that is clearer or not. But it avoids the repetition.
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Subject: [Bug c++/53822] spell out typedefs in ambiguous call
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

--- Comment #6 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #5)
> (In reply to Marc Glisse from comment #4)
> There is code in error.c:type_to_string to print "{aka ". It does some
> tricks to avoid printing aka when there are no typedefs. Perhaps
> args_to_string() should call type_to_string() instead of calling dump_type
> directly. With that, it prints:
> 
> test.cc:6:6: error: call of overloaded ‘f(NT& {aka unsigned int&})’ is
> ambiguous

Nice!

> I am not sure if that is clearer or not.

Probably depends on cases. Sometimes it is good to have the explanation right
next to the type, other times it takes up all the space and you can't even find
the commas separating the arguments anymore (maybe if the whole {aka ...} block
was a different color?).
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idT570

--- Comment #15 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Note, this fix had PR59362 as follow-up.

[Bug c++/53822] spell out typedefs in ambiguous call

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

--- Comment #7 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #6)
> Probably depends on cases. Sometimes it is good to have the explanation
> right next to the type, other times it takes up all the space and you can't
> even find the commas separating the arguments anymore (maybe if the whole
> {aka ...} block was a different color?).

That could be possible. On the other hand, the "{aka ...}" thing is not really
ideal (in general). Currently,

1) It is not translated
2) You need to know what "aka" means (not obvious relation with 'typedef')
3) It is not correctly quoted, that is, instead of "`NT {aka int}'", we should
print "`NT' {aka `int'}".
4) The "aka" should not be colored in the same way as the types. Fixing the
quoting will fix this.
5) Complex declarations lead to many repetitions of "aka": "`f(NT {aka int},UT
{aka unsigned int},DT {aka double int})'".
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY252

janus at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
                 CC|                            |janus at gcc dot gnu.org
            Summary|wrong code generation for   |wrong code generation for
                   |allocatable dummy arguments |allocatable character
                   |                            |component

--- Comment #2 from janus at gcc dot gnu.org ---
Unrelated to dummy arguments. Reduced test case:


  implicit none

  type branch_plot_results_ppv_type
     character, allocatable :: label
  end type

  type(branch_plot_results_ppv_type), allocatable :: appv(:)

  allocate(appv(2))

end

[Bug c++/53822] spell out typedefs in ambiguous call

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2013-04-16 00:00:00         |2021-8-9

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
clang does not even print out the argument type :).
NOTE that is actually worse.
ICC and MSVC both print out the typedef name.

[Bug c++/53822] spell out typedefs in ambiguous call

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53822

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement