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.

2 files changed, 4 insertions, 4 deletions

diff --git a/src/libcore/tests/nonzero.rs b/src/libcore/tests/nonzero.rs
index 588fffda35f..a795dd57504 100644
--- a/src/libcore/tests/nonzero.rs
+++ b/src/libcore/tests/nonzero.rs
@@ -16,7 +16,7 @@ use std::mem::size_of;
 #[test]
 fn test_create_nonzero_instance() {
     let _a = unsafe {
-        NonZero::new(21)
+        NonZero::new_unchecked(21)
     };
 }
 
@@ -28,14 +28,14 @@ fn test_size_nonzero_in_option() {
 #[test]
 fn test_match_on_nonzero_option() {
     let a = Some(unsafe {
-        NonZero::new(42)
+        NonZero::new_unchecked(42)
     });
     match a {
         Some(val) => assert_eq!(val.get(), 42),
         None => panic!("unexpected None while matching on Some(NonZero(_))")
     }
 
-    match unsafe { Some(NonZero::new(43)) } {
+    match unsafe { Some(NonZero::new_unchecked(43)) } {
         Some(val) => assert_eq!(val.get(), 43),
         None => panic!("unexpected None while matching on Some(NonZero(_))")
     }
diff --git a/src/libcore/tests/ptr.rs b/src/libcore/tests/ptr.rs
index e28dc6a6881..c2d53840f8f 100644
--- a/src/libcore/tests/ptr.rs
+++ b/src/libcore/tests/ptr.rs
@@ -167,7 +167,7 @@ fn test_set_memory() {
 #[test]
 fn test_unsized_unique() {
     let xs: &[i32] = &[1, 2, 3];
-    let ptr = unsafe { Unique::new(xs as *const [i32] as *mut [i32]) };
+    let ptr = unsafe { Unique::new_unchecked(xs as *const [i32] as *mut [i32]) };
     let ys = unsafe { ptr.as_ref() };
     let zs: &[i32] = &[1, 2, 3];
     assert!(ys == zs);