[Bug c++/70637] New: Ambiguity error invoking a constructor with double brace initialization

[steveire at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70637

            Bug ID: 70637
           Summary: Ambiguity error invoking a constructor with double
                    brace initialization
           Product: gcc
           Version: 5.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: steveire at gmail dot com
  Target Milestone: ---

$ g++ --version
g++ (Ubuntu 5.2.1-22ubuntu2) 5.2.1 20151010
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++ double-braces.cpp -std=c++11
double-braces.cpp: In function ‘int main()’:
double-braces.cpp:16:20: error: call of overloaded ‘SomeClass(<brace-enclosed
initializer list>)’ is ambiguous
   SomeClass sc({{}});
                    ^
double-braces.cpp:7:12: note: candidate:
SomeClass::SomeClass(std::vector<std::vector<float> >)
   explicit SomeClass(std::vector<std::vector<float>> samples)
            ^
double-braces.cpp:4:7: note: candidate: SomeClass::SomeClass(const SomeClass&)
 class SomeClass
       ^
double-braces.cpp:4:7: note: candidate: SomeClass::SomeClass(SomeClass&&)
$ cat double-braces.cpp 

#include <vector>

class SomeClass
{
public:
  explicit SomeClass(std::vector<std::vector<float>> samples)
    : mSamples(std::move(samples))
  {
  }
  std::vector<std::vector<float>> mSamples;
};

int main()
{
  SomeClass sc({{}});
}