P3948R1 — constant_wrapper is the only tool needed for passing constant expressions
LWG
```cpp "int std:: __polyfunc :: _Base_invoker <false , int >:: _S_call_storage < …" jmp [QWORD PTR [rdi]] "int std:: __polyfunc :: _Base_invoker <false , int >:: _S_call_storage < …" mov eax , 2 ret ```