StableMir will emit no body for functions that are magic in rustc

[zjp-CN]

{
  "def_id": "DefId { id: 22, name: \"std::ptr::drop_in_place\" }",
  "func": "pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T)"
}

For drop_in_place, the source code is

#[stable(feature = "drop_in_place", since = "1.8.0")]
#[lang = "drop_in_place"]
#[allow(unconditional_recursion)]
#[rustc_diagnostic_item = "ptr_drop_in_place"]
pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
    // Code here does not matter - this is replaced by the
    // real drop glue by the compiler.

    // SAFETY: see comment above
    unsafe { drop_in_place(to_drop) }
}