[Bug c++/79661] New: Bogus "destructor is private within this context" only in C++17 mode

[sbergman at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79661

            Bug ID: 79661
           Summary: Bogus "destructor is private within this context" only
                    in C++17 mode
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sbergman at redhat dot com
  Target Milestone: ---

At least with a recent GCC trunk build:

> $ g++ --version
> g++ (GCC) 7.0.1 20170220 (experimental)
> Copyright (C) 2017 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
> $ cat test.cc
> template<typename T> struct R { R(T *); };
> struct S {
>  S(int);
> private:
>  ~S();
> };
> void f() { R<S>(new S(0)); }
> 
> $ g++ -std=c++17 -fsyntax-only test.cc
> test.cc: In function ‘void f()’:
> test.cc:7:24: error: ‘S::~S()’ is private within this context
>  void f() { R<S>(new S(0)); }
>                         ^
> test.cc:5:2: note: declared private here
>   ~S();
>   ^

Compilation succeeds when dropping the S constructor's int parameter (or even
merely giving it a default value and removing the argument from 'new S()'), or
when dropping the R<S>(...) wrapper, or when compiling as -std=c++14, or when
compiling with GCC 6.3.1 (gcc-c++-6.3.1-1.fc25.x86_64).  So I assume this is a
bug rather than an actual C++17 requirement that I'm not aware of.

(The used GCC trunk version already includes the fix for somewhat-similar bug
78469.)