https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96815
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |ice-on-invalid-code
Last reconfirmed| |2020-08-27
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
#include <iostream>
#include <string>
#include <variant>
#include <tuple>
template<typename T>
struct A { // evtHandler
using type = T;
void doStuff(T thing) { std::cout << "nice T ! " << thing << std::endl; }
};
template<typename ...args>
struct B { // module
std::tuple<args...> As;
B(args... _As) : As{std::make_tuple(_As...)}{};
template<typename K>
void dispatch(K coolObject) {
// doStuff for As that match
std::apply([&](auto& ... a) {
([&]{if constexpr(std::is_same_v<typename decltype(a)::type, K>) {
a.doStuff(coolObject); }}(), ...);
}, As);
}
};
template<typename ...bees>
struct C { // controller
std::tuple<bees...> Bs;
C(bees... _Bs) : Bs{_Bs...} {};
template<typename L>
void fullDispatch(L veryCoolObject) {
// doStuff for all Bs that match
std::apply([&](auto& ... b) {
(b.dispatch(veryCoolObject), ...);
}, Bs);
}
};
int main() {
auto b1 = B{A<int>{}, A<float>{}, A<double>{}};
auto b2 = B{A<double>{}, A<char>{}, A<bool>{}};
auto c = C{b1, b2};
c.fullDispatch(12.5);
}
ICEs with -std=gnu++17
96815.C: In instantiation of 'B<args>::dispatch<double>::<lambda(auto:22& ...)>
[with auto:22 = {A<int>, A<float>, A<double>}]':
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:2506:26: required by
substitution of 'template<class _Fn, class ... _Args> static
std::__result_of_success<decltype (declval<_Fn>()((declval<_Args>)()...)),
std::__invoke_other> std::__result_of_other_impl::_S_test(int) [with _Fn =
B<args>::dispatch<double>::<lambda(auto:22& ...)>; _Args = {A<int>&, A<float>&,
A<double>&}]'
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:2517:55: required from
'struct std::__result_of_impl<false, false,
B<args>::dispatch<double>::<lambda(auto:22& ...)>, A<int>&, A<float>&,
A<double>&>'
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:2522:12: required from
'struct std::__invoke_result<B<args>::dispatch<double>::<lambda(auto:22& ...)>,
A<int>&, A<float>&, A<double>&>'
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:138:12: required from
'struct
std::__and_<std::__is_invocable_impl<std::__invoke_result<B<args>::dispatch<double>::<lambda(auto:22&
...)>, A<int>&, A<float>&, A<double>&>, void, true, void>,
std::__call_is_nothrow<std::__invoke_result<B<args>::dispatch<double>::<lambda(auto:22&
...)>, A<int>&, A<float>&, A<double>&>,
B<args>::dispatch<double>::<lambda(auto:22& ...)>, A<int>&, A<float>&,
A<double>&> >'
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:2979:12: [ skipping 7
instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:138:12: recursively
required by substitution of 'template<class _Result, class _Ret> struct
std::__is_invocable_impl<_Result, _Ret, true, std::__void_t<typename
_CTp::type> > [with _Result =
std::__invoke_result<C<bees>::fullDispatch<double>::<lambda(auto:23& ...)>,
B<A<int>, A<float>, A<double> >&, B<A<double>, A<char>, A<bool> >&>; _Ret =
void]'
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:138:12: required from
'struct
std::__and_<std::__is_invocable_impl<std::__invoke_result<C<bees>::fullDispatch<double>::<lambda(auto:23&
...)>, B<A<int>, A<float>, A<double> >&, B<A<double>, A<char>, A<bool> >&>,
void, true, void>,
std::__call_is_nothrow<std::__invoke_result<C<bees>::fullDispatch<double>::<lambda(auto:23&
...)>, B<A<int>, A<float>, A<double> >&, B<A<double>, A<char>, A<bool> >&>,
C<bees>::fullDispatch<double>::<lambda(auto:23& ...)>, B<A<int>, A<float>,
A<double> >&, B<A<double>, A<char>, A<bool> >&> >'
/home/jwakely/gcc/10/include/c++/10.2.1/type_traits:2979:12: required from
'struct
std::is_nothrow_invocable<C<bees>::fullDispatch<double>::<lambda(auto:23&
...)>, B<A<int>, A<float>, A<double> >&, B<A<double>, A<char>, A<bool> >&>'
/home/jwakely/gcc/10/include/c++/10.2.1/tuple:1707:31: required from
'constexpr const bool std::__unpack_std_tuple<template<class _Fn, class ...
_ArgTypes> struct std::is_nothrow_invocable,
C<bees>::fullDispatch<double>::<lambda(auto:23& ...)>, std::tuple<B<A<int>,
A<float>, A<double> >, B<A<double>, A<char>, A<bool> > >&>'
/home/jwakely/gcc/10/include/c++/10.2.1/tuple:1730:14: required from
'constexpr decltype(auto) std::apply(_Fn&&, _Tuple&&) [with _Fn =
C<bees>::fullDispatch<double>::<lambda(auto:23& ...)>; _Tuple =
std::tuple<B<A<int>, A<float>, A<double> >, B<A<double>, A<char>, A<bool> >
>&]'
96815.C:35:19: required from 'void C<bees>::fullDispatch(L) [with L = double;
bees = {B<A<int>, A<float>, A<double> >, B<A<double>, A<char>, A<bool> >}]'
96815.C:48:24: required from here
96815.C:20:30: internal compiler error: in tsubst_pack_expansion, at
cp/pt.c:12928
20 | std::apply([&](auto& ... a) {
| ~~~~~~^~~~~
0x5c4e33 tsubst_pack_expansion(tree_node*, tree_node*, int, tree_node*)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:12928
0x729a55 tsubst_decl
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:14243
0x73162b tsubst_pack_expansion(tree_node*, tree_node*, int, tree_node*)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:12849
0x738f82 tsubst_fold_expr_pack
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:12462
0x738f82 tsubst_unary_right_fold
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:12578
0x738f82 tsubst_copy
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:16983
0x72cd68 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:20567
0x724f84 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:19160
0x724f84 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:18773
0x72613c tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17840
0x72613c tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17885
0x7267ae tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17840
0x7267ae tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17855
0x725b2b tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17840
0x725b2b tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:18174
0x725b2b tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17840
0x725b2b tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:18174
0x7267ae tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17840
0x7267ae tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17855
0x725b2b tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
/home/jwakely/src/gcc/gcc-10/gcc/cp/pt.c:17840
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Clang rejects it as invalid:
<source>:21:55: error: type 'decltype(a)' (aka 'A<bool> &') cannot be used
prior to '::' because it has no members
([&]{if constexpr(std::is_same_v<typename decltype(a)::type, K>) {
a.doStuff(coolObject); }}(), ...);
^
