https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90448
Bug ID: 90448
Summary: [8/9/10 Regression] decltype-based lambda parameter
pack is rejected
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: asolokha at gmx dot com
CC: jakub at gcc dot gnu.org, jason at gcc dot gnu.org,
webrown.cpp at gmail dot com
Target Milestone: ---
+++ This bug was initially created as a clone of Bug #90172 +++
g++ rejects the following testcase which is believed to be valid:
template<class ... Ts> int fooV(Ts ... ts) {
auto L = [](auto ... a) {
auto M = [](decltype(a) ... b) -> void {
};
return M;
};
decltype(L(L, ts...)) (*fp)(decltype(L), decltype(ts) ...) = L;
return 0;
}
int run2 = fooV("BC", 3, 2.77, 'A', float{}, short{}, unsigned{});
% g++-10.0.0-alpha20190512 -std=c++17 -c mziudrma.cpp
mziudrma.cpp: In instantiation of 'int fooV(Ts ...) [with Ts = {const char*,
int, double, char, float, short int, unsigned int}]':
mziudrma.cpp:13:65: required from here
mziudrma.cpp:3:14: error: expansion pattern 'decltype (#'nontype_argument_pack'
not supported by dump_expr#<expression error>)' contains no parameter packs
3 | auto M = [](decltype(a) ... b) -> void {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 | };
| ~
