https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70585
Bug ID: 70585
Summary: Bogus 'ambiguous template instantiation' error with
partial specializations involving a pack expansion
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rs2740 at gmail dot com
Target Milestone: ---
Repro:
template<class> class meow;
template<class...> struct purr;
template<class T, class... Ts>
struct purr<T, meow<Ts>...> {};
template<class... Ts>
struct purr<int, meow<Ts>...> {};
template struct purr<int, meow<int>>;
gcc HEAD 6.0.0 20160407 (experimental) on Wandbox prints:
prog.cc:10:17: error: ambiguous template instantiation for 'struct purr<int,
meow<int> >'
template struct purr<int, meow<int>>;
^~~~~~~~~~~~~~~~~~~~
prog.cc:6:8: note: candidates are: template<class T, class ... Ts> struct
purr<T, meow<Ts>...> [with T = int; Ts = {int}]
struct purr<T, meow<Ts>...> {};
^~~~~~~~~~~~~~~~~~~~
prog.cc:8:8: note: template<class ... Ts> struct purr<int,
meow<Ts>...> [with Ts = {int}]
struct purr<int, meow<Ts>...> {};
^~~~~~~~~~~~~~~~~~~~~~
prog.cc:10:17: error: explicit instantiation of 'struct purr<int, meow<int> >'
before definition of template
template struct purr<int, meow<int>>;
^~~~~~~~~~~~~~~~~~~~
Clang compiles this code.
