https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120259
Bug ID: 120259
Summary: Using Incomplete&& as argument in
invoke_r/move_only_function fails to compile
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: tkaminsk at gcc dot gnu.org
Target Milestone: ---
Passing rvalue reference to incomplete type or instantiating move_only_function
with it as parameter produces ill-formed program.
```
struct Incomplete;
int foo(Incomplete& i);
void bar(Incomplete& i) {
std::invoke_r<int>(&foo, std::move(i)); // ILL-FORMED
std::move_only_function<int(Incomplete&&)> mo(&foo); // ILL-FORMED
}
```
See: https://godbolt.org/z/GvW7veGKa
The error produced is:
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:3055:53:
error: static assertion failed: each argument type must be a complete class or
an unbounded array
3055 | static_assert((std::__is_complete_or_unbounded(
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
3056 | __type_identity<_ArgTypes>{}) && ...),
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The failure in `move_only_function` is due instantiation of std::invoke_r.
