error[E0277]: can't compare `*const ()` with `*const ()` in const contexts
  --> $DIR/issue-25826.rs:3:52
   |
LL |     const A: bool = unsafe { id::<u8> as *const () < id::<u16> as *const () };
   |                                                    ^ no implementation for `*const () < *const ()` and `*const () > *const ()`
   |
   = help: the trait `~const PartialOrd` is not implemented for `*const ()`
note: the trait `PartialOrd` is implemented for `*const ()`, but that implementation is not `const`
  --> $DIR/issue-25826.rs:3:52
   |
LL |     const A: bool = unsafe { id::<u8> as *const () < id::<u16> as *const () };
   |                                                    ^
help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
   |
LL | fn main() where *const (): ~const PartialOrd {
   |           ++++++++++++++++++++++++++++++++++

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.