sub_ptr() is equivalent to usize::try_from().unwrap_unchecked(), not usize::from().unwrap_unchecked().

`usize::from()` gives a `usize`, not `Result<usize>`, and `usize: From<isize>` is not implemented.

Author: ChayimFriedman2

library/core/src/ptr/const_ptr.rs

@@ -731,7 +731,7 @@ impl<T: ?Sized> *const T {
     /// This computes the same value that [`offset_from`](#method.offset_from)
     /// would compute, but with the added precondition that the offset is
     /// guaranteed to be non-negative.  This method is equivalent to
-    /// `usize::from(self.offset_from(origin)).unwrap_unchecked()`,
+    /// `usize::try_from(self.offset_from(origin)).unwrap_unchecked()`,
     /// but it provides slightly more information to the optimizer, which can
     /// sometimes allow it to optimize slightly better with some backends.
     ///

library/core/src/ptr/mut_ptr.rs

@@ -904,7 +904,7 @@ impl<T: ?Sized> *mut T {
     /// This computes the same value that [`offset_from`](#method.offset_from)
     /// would compute, but with the added precondition that the offset is
     /// guaranteed to be non-negative.  This method is equivalent to
-    /// `usize::from(self.offset_from(origin)).unwrap_unchecked()`,
+    /// `usize::try_from(self.offset_from(origin)).unwrap_unchecked()`,
     /// but it provides slightly more information to the optimizer, which can
     /// sometimes allow it to optimize slightly better with some backends.
     ///