https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89687
Bug ID: 89687
Summary: Empty pack expansion in `decltype` results in cryptic
compiler error (dump_expr)
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: vittorio.romeo at outlook dot com
Target Milestone: ---
Consider the following code:
template <typename F>
void foo(F f)
{
[f](auto... xs)
{
[xs...]() -> decltype(f(xs...)) { };
};
}
int main()
{
foo([]{ });
}
Live example on godbolt.org:
https://gcc.godbolt.org/z/DTC3f6
It compiles under clang++ trunk, but fails to compile under g++ trunk (9.0.1
20190311) with the following error:
<source>: In instantiation of 'void foo(F) [with F = main()::<lambda()>]':
<source>:12:14: required from here
<source>:6:32: error: expansion pattern '#'nontype_argument_pack' not
supported by dump_expr#<expression error>' contains no parameter packs
6 | [xs...]() -> decltype(f(xs...)) { };
| ~^~~~~~~
Compiler returned: 1
