https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125591
Bug ID: 125591
Summary: ICE in tsubst_pack_expansion with C++26 structured
binding packs and fold expressions
Product: gcc
Version: 16.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: willsmithofficial2222 at gmail dot com
Target Milestone: ---
Created attachment 64618
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64618&action=edit
Preprocessed source file
An internal compiler error occurs when attempting to expand a structured
binding pack directly into a fold expression.
The following code compiles with Clang, but fails with all GCC 16.1.0 (and
trunk) compilers available on godbolt.org:
template<typename T, typename U>
concept is_same_v = __is_same(T, U);
struct Vec3 { int x, y, z; };
template<class V>
consteval bool hasSameTypes() {
constexpr auto [...Ms] = V{};
using T = decltype(Ms...[0]);
// ICE: in tsubst_pack_expansion, at cp/pt.cc:14250
return (is_same_v<decltype(Ms), T> && ...);
// Workaround:
// return []<class... Ts> { return (is_same_v<Ts, T> && ...); }.template
operator()<decltype(Ms)...>();
}
int main() {
return hasSameTypes<Vec3>() ? 0 : 1;
}
Compiler flags: -std=c++26 -Wall -Werror
Godbolt link: https://godbolt.org/z/jh8n6PPTv
