Re: [Boost-bugs] [Boost C++ Libraries] #3270: Ambiguous conversion, even though no conversion exists

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #3270: Ambiguous conversion, even though no conversion exists
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-07-17 16:20:55

#3270: Ambiguous conversion, even though no conversion exists
-------------------------------------------------+--------------------------
 Reporter:  Olaf Lenz <lenzo@…>                  |       Owner:  dgregor 
     Type:  Bugs                                 |      Status:  new     
Milestone:  Boost 1.40.0                         |   Component:  function
  Version:  Boost 1.39.0                         |    Severity:  Problem 
 Keywords:                                       |  
-------------------------------------------------+--------------------------

Comment(by steven_watanabe):

 Replying to [ticket:3270 Olaf Lenz <lenzo@…>]:
 > Unfortunately,
 > in this case, there does not even exist a conversion from "class A" to
 the
 > function type! To test that, just comment the first definition of
 B::f():


 Any type can be converted to a boost::function.
 The declaration of the conversion always exists,
 which is all that the compiler checks for in overload
 resolution.  The conversion doesn't compile unless
 the type has a function call operator.

 > I think that this can be considered a bug. Or what else can I do in this
 case?

 Did you really intend to make the overload for A const
 and the overload for boost::function non-const?

 The following compiles for me

 {{{
 #include <boost/function.hpp>

 struct A {};

 struct B {
   void f(const A &a) const {}
   void f(boost::function< void () > a) const {}
 };

 int main() {
   A a;
   B b;
   b.f(a);
 }

 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3270#comment:1>
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