[Bug c++/102338] Recursive noexcept specification inside class/struct

[jergussuja at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102338

--- Comment #4 from Jerguš Suja <jergussuja at gmail dot com> ---
gcc version 9.3.0

x86_64-linux-gnu

Configured with: ../src/configure -v --with-pkgversion='Ubuntu 9.3.0-10ubuntu2'
--with-bugurl=file:///usr/share/doc/gcc-9/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,gm2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-9
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new
--enable-gnu-unique-object --disable-vtable-verify --enable-plugin
--enable-default-pie --with-system-zlib --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic --enable-offload-targets=nvptx-none,hsa
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu

Code that trigger compilation failed:

struct S {

    template<typename T>
    static auto f(T && t) noexcept {
        return true;
    }

    template<typename T, typename... Ts>
    static auto f(T && t, Ts && ... ts) noexcept(noexcept(f(ts...))) {
        return f(ts...);
    }

};

int main() {
    S::f(true, 0, 5u);
    return 0;
}

Compiler error:

bug.cpp: In instantiation of ‘static auto S::f(T&&, Ts&& ...) [with T = bool;
Ts = {int, unsigned int}]’:
bug.cpp:16:21:   required from here
bug.cpp:9:60: error: no matching function for call to ‘S::f(int&, unsigned
int&)’
    9 |     static auto f(T && t, Ts && ... ts) noexcept(noexcept(f(ts...))) {
      |                                                           ~^~~~~~~
bug.cpp:4:17: note: candidate: ‘template<class T> static auto S::f(T&&)’
    4 |     static auto f(T && t) noexcept {
      |                 ^
bug.cpp:4:17: note:   template argument deduction/substitution failed:
bug.cpp:9:60: note:   candidate expects 1 argument, 2 provided
    9 |     static auto f(T && t, Ts && ... ts) noexcept(noexcept(f(ts...))) {
      |                                                           ~^~~~~~~

GCC version 7.5 compile this, but version 8 and more does not. If I declare
function 'f' in scope of class or struct, it should be visible everywhere
inside class/struct scope. Also in noexcept specifier (it should not matter if
it is recursive call). MSVC v19.28 and Clang 12.0.1 accept this and compile
this code.