[Bug c++/67274] New: Inconsistent `this->` required when calling member function in a lambda capturing `this` through another function

[vittorio.romeo at outlook dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67274

            Bug ID: 67274
           Summary: Inconsistent `this->` required when calling member
                    function in a lambda capturing `this` through another
                    function
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vittorio.romeo at outlook dot com
  Target Milestone: ---

Passing a `this`-capturing generic lambda (to a template function) that calls a
member function of `this` without an explicit `this->` results in an error:

error: cannot call member function 'void Example::foo(int)' without object     
 call([this](auto x){ foo(x); });`

If the lambda is not generic, or if the lambda is not passed to any other
function but called in place, it compiles without an explicit `this->`. 

For reference, clang 3.6+ is cool with the code in all situations.

---

Minimal example:
http://melpon.org/wandbox/permlink/M2eH3FUOentPfieM

template<typename TF>
void call(TF&& f)
{
    f(1);   
}

struct Example
{        
    void foo(int){ }

    void bar()
    {
        call([this](auto x){ foo(x); });
    }
};

int main()
{
    Example{}.bar();
    return 0;
}

---

StackOverflow question with more examples:
http://stackoverflow.com/questions/32097759