[Bug c++/58930] New: [C++11] Bogus error: converting to ... from initializer list would use explicit constructor

[ppluzhnikov at google dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58930

            Bug ID: 58930
           Summary: [C++11] Bogus error: converting to ... from
                    initializer list would use explicit constructor
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ppluzhnikov at google dot com

Google ref: b/11448857

This is somewhat similar to PR54835.

// ---
struct SampleModule
{
   explicit SampleModule (int);
};

template < typename >
struct BaseHandler
{
#ifndef BUG
   BaseHandler ();
#endif
   SampleModule module_ { 0 };
};

BaseHandler<int> a;
// ---

Clang compiles either variant.
Trunk GCC (g++ (GCC) 4.9.0 20131028 (experimental)):

g++ -c -std=c++11 t.cc && echo ok && g++ -c -std=c++11 t.cc -DBUG
ok
t.cc: In constructor 'constexpr BaseHandler<int>::BaseHandler()':
t.cc:7:8: error: converting to 'SampleModule' from initializer list would use
explicit constructor 'SampleModule::SampleModule(int)'
 struct BaseHandler
       ^
t.cc: At global scope:
t.cc:15:18: note: synthesized method 'constexpr
BaseHandler<int>::BaseHandler()' first required here
 BaseHandler<int> a;
                 ^

Making BaseHandler a non-template class also makes the problem go away.