[Bug c++/87651] New: inner class with template template friend declaration of same name fails to compile in gcc 8.1, 8.2, and 9.0

[haining.cpp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87651

            Bug ID: 87651
           Summary: inner class with template template friend declaration
                    of same name fails to compile in gcc 8.1, 8.2, and 9.0
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haining.cpp at gmail dot com
  Target Milestone: ---

Requirements to repro

1) Outer class must be template
2) Inner class must have template template parameter

#### Sample program ####

template <typename> class Cls;

template <typename>
struct Outer {
  template <template <typename> class>
  class Failure {
    template <template <typename> class>
    friend class Failure; // All Failures should be friends
  };

  using F = Failure<Cls>;
};

int main() {
  Outer<void>::F var;
}


#### Error message #####

prog.cc: In instantiation of 'class Outer<void>::Failure<Cls>':
prog.cc:15:18:   required from here
prog.cc:5:33: error: template parameter 'template<class> template<class>
class<template-parameter-2-1>'
   template <template <typename> class>
                                 ^~~~~
prog.cc:8:18: error: redeclared here as 'template<class>
class<template-parameter-1-1>'
     friend class Failure;
                  ^~~~~~~

#### Additional Info ####


wandbox links to errors:

 - [gcc-8.1.0](https://wandbox.org/permlink/vpzvcXcPUwVm4ent)
 - [gcc-8.2.0](https://wandbox.org/permlink/YaD9sml3aPaJExcm)
 - [gcc HEAD 9.0.0 20181017 ](https://wandbox.org/permlink/FXqrijJRqbyNT0ZT)

passing with [gcc-7.3.0](https://wandbox.org/permlink/0HQ9K8PuSJBqRmD1)


This is causing several components of
http://github.com/ryanhaining/cppitertools to fail to compile, and I have no
ideas for a workaround besides making my data members public