[Bug c++/62085] New: SFINAE where specialization parameter class member returns an abstract type fails

[jameslyon0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62085

            Bug ID: 62085
           Summary: SFINAE where specialization parameter class member
                    returns an abstract type fails
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jameslyon0 at gmail dot com

The attached code fails to compile with:

sfinae.cpp: In instantiation of ‘struct A<C>’:
sfinae.cpp:14:8:   required from here
sfinae.cpp:3:5: error: invalid abstract return type ‘C’
   T f();
     ^
sfinae.cpp:9:8: note:   because the following virtual functions are pure within
‘C’:
 struct C {
        ^
sfinae.cpp:10:11: note:     virtual C::~C()
   virtual ~C() = 0;


I'm not an expert on the C++ standard, but I would expect the partial
specialization of B to be excluded by SFINAE rather than getting a compiler
error (clang accepts the code).

Looking at previous bugs, it seems that #12672 might be related.