[Bug c++/57543] New: decltype needs eplicity 'this' pointer in member function declaration of template class with trailing return type

[mitchnull+gcc at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57543

            Bug ID: 57543
           Summary: decltype needs eplicity 'this' pointer in member
                    function declaration of template class with trailing
                    return type
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mitchnull+gcc at gmail dot com

Created attachment 30268
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30268&action=edit
decltype-implicit-this.cpp

When using trailing return-type for member functions of a template class, the
'this' pointer must be explicitly mentioned. This should not be necessary (The
implicit 'this' works with a non-template class).

Example:

emplate <typename T>
struct DecltypeConstThis {

    T f() const { return T{}; }

    auto g() -> decltype(this->f()) { return this->f(); }
    auto h() const  ->  decltype(f()) { return f(); } // this should work the
same as g() above (with implicit 'this')

};

struct Working {
    int f() const { return 0; }
    auto h() const -> decltype(f()) { return 0; }
};


int main() {

    Working w;
    w.h();

    DecltypeConstThis<int> d;
    d.g();
    d.h();

    return 0;
}

compiler output:

[mitch@deneb src]$ g++ -std=c++11 -o decltype-implicit-this
decltype-implicit-this.cpp 
decltype-implicit-this.cpp: In instantiation of ‘struct
DecltypeConstThis<int>’:
decltype-implicit-this.cpp:22:28:   required from here
decltype-implicit-this.cpp:7:36: error: cannot call member function ‘T
DecltypeConstThis<T>::f() const [with T = int]’ without object
     auto h() const  ->  decltype(f()) { return f(); } // this should work the
same as g() above (with implicit 'this')
                                    ^
decltype-implicit-this.cpp: In function ‘int main()’:
decltype-implicit-this.cpp:24:7: error: ‘struct DecltypeConstThis<int>’ has no
member named ‘h’
     d.h();
       ^

ps: possibly related to bug #54359