https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96815
Jason Cobb <jason.e.cobb at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jason.e.cobb at gmail dot com
--- Comment #2 from Jason Cobb <jason.e.cobb at gmail dot com> ---
I think I've stumbled upon this and have a reduced version with the same
elements (constexpr if in a lambda in a pack expansion in a lambda in a
template).
Source w/ -std=c++17:
////////
template<typename>
inline constexpr auto true_v = true;
template<typename>
auto test() {
return [](auto... x) {
([]{ if constexpr (true_v<decltype(x)>); }, ...);
}();
}
auto foo() {
test<void>();
}
END SOURCE
Compiler output:
<source>: In instantiation of 'test<void>::<lambda(auto:1 ...)> [with auto:1 =
{}]':
<source>:8:6: required from 'auto test() [with <template-parameter-1-1> =
void]'
<source>:12:16: required from here
<source>:6:19: internal compiler error: in tsubst_pack_expansion, at
cp/pt.c:12952
6 | return [](auto... x) {
| ~~~~^~~~~
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://gcc.gnu.org/bugs/> for instructions.
END COMPILER OUTPUT
Seen on Compiler Explorer: https://godbolt.org/z/jqEP65
This appears to ICE back through to 8.1 (as tested on Compiler Explorer). Clang
trunk accepts as valid.
GCC does not ICE if "test" is not a template or if the body of the outer-most
lambda is placed into a separate function.
