https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102678
Bug ID: 102678
Summary: GCC fails to compile immediately invoked lambda inside
fold expression
Product: gcc
Version: 11.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: michael.gerhold at web dot de
Target Milestone: ---
The following code
#include <variant>
#include <iostream>
#include <string>
template<typename... T>
void printAlternatives([[maybe_unused]] const std::variant<T...>& variant)
{
([&]() {
// holds_alternative<T>(variant); // <- enable to make it compile
T element{};
std::cout << element << "\n";
}(), ...);
}
int main() {
std::variant<std::string, int, float> variant;
printAlternatives(variant);
}
does not compile and gives the following error message:
error: operand of fold expression has no unexpanded parameter packs
But the code does compile both on MSVC and Clang.
Live example on compiler explorer: https://godbolt.org/z/zEqW4njW3
