Auto merge of #46094 - dtolnay:is_null, r=alexcrichton

Remove `T: Sized` on `ptr::is_null()`

Originally from #44932 -- this is purely a revert of the last commit of that PR, which was removing some changes from the previous commits in the PR. So a revert of a revert means this is code written by @cuviper!

@mikeyhew makes a compelling case in https://github.com/rust-lang/rfcs/issues/433#issuecomment-345495505 for why this is the right way to implement `is_null` for trait objects. And the behavior for slices makes sense to me as well.

```diff
  impl<T: ?Sized> *const T {
-     pub fn is_null(self) -> bool where T: Sized;
+     pub fn is_null(self) -> bool;
  }

  impl<T: ?Sized> *mut T {
-     pub fn is_null(self) -> bool where T: Sized;
+     pub fn is_null(self) -> bool;
  }

0 files changed, 0 insertions, 0 deletions