Rollup merge of #42959 - SimonSapin:nonzero-checked, r=sfackler

Make the "main" constructors of NonZero/Shared/Unique return Option

Per discussion in https://github.com/rust-lang/rust/issues/27730#issuecomment-303939441.

This is a breaking change to unstable APIs.

The old behavior is still available under the name `new_unchecked`. Note that only that one can be `const fn`, since `if` is currently not allowed in constant contexts.

In the case of `NonZero` this requires adding a new `is_zero` method to the `Zeroable` trait. I mildly dislike this, but it’s not much worse than having a `Zeroable` trait in the first place. `Zeroable` and `NonZero` are both unstable, this can be reworked later.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index 06f4f7643ec..3844690860b 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -44,7 +44,7 @@ impl TaggedHashUintPtr {
     #[inline]
     unsafe fn new(ptr: *mut HashUint) -> Self {
         debug_assert!(ptr as usize & 1 == 0 || ptr as usize == EMPTY as usize);
-        TaggedHashUintPtr(Unique::new(ptr))
+        TaggedHashUintPtr(Unique::new_unchecked(ptr))
     }
 
     #[inline]
@@ -56,7 +56,7 @@ impl TaggedHashUintPtr {
             } else {
                 usize_ptr &= !1;
             }
-            self.0 = Unique::new(usize_ptr as *mut HashUint)
+            self.0 = Unique::new_unchecked(usize_ptr as *mut HashUint)
         }
     }
 
@@ -877,7 +877,7 @@ impl<K, V> RawTable<K, V> {
                 elems_left: elems_left,
                 marker: marker::PhantomData,
             },
-            table: unsafe { Shared::new(self) },
+            table: Shared::from(self),
             marker: marker::PhantomData,
         }
     }