[Bug c++/79308] New: Internal compilation error on specialization of nested template classes

[bjhend@sags-per-mail.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79308

            Bug ID: 79308
           Summary: Internal compilation error on specialization of nested
                    template classes
           Product: gcc
           Version: 6.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bjhend@sags-per-mail.de
  Target Milestone: ---

Created attachment 40639
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40639&action=edit
Source code

The following code (attached as element.cpp) causes the error

        internal compiler error: in finish_member_declaration, at
cp/semantics.c:2966

when compiled by calling

        gcc -v -save-temps -Wall -Wextra -std=c++11  element.cpp

with GCC 6.3.0. The nearly same error is caused by GCC 5.4.1 and GCC 4.8.


---------------------------------------
template <class>
struct Element
{
        Element(void)
        {
                WriteOutput<int>();
        }

        template <typename>
        struct WriteOutput
        {
        };
};


template <>
template <typename InnerType>
struct Element<int>::WriteOutput<InnerType>
{                                       // line mentioned in error message
        void foo(void)
        {
        }

        virtual void bar(void)
        {
        }
};


Element<int> e;
---------------------------------------


The error disappears on each of the following changes:

* Remove one of the element functions in the specialization.

* Remove the "virtual" of all element functions.

* Make the specialized type-argument of the outer template different from the
unspecialized template type-argument of the nested template. As long as they
are the same, no matter which actually, the error is triggered.

In these case the compiler complains correctly about the missing main function.

If I find out how to attach another file I will attach the whole compiler
output.