refactor: moved IsZero into is_zero.rs

library/alloc/src/vec/is_zero.rs

@@ -0,0 +1,71 @@
+use crate::boxed::Box;
+
+#[rustc_specialization_trait]
+pub(super) unsafe trait IsZero {
+    /// Whether this value is zero
+    fn is_zero(&self) -> bool;
+}
+
+macro_rules! impl_is_zero {
+    ($t:ty, $is_zero:expr) => {
+        unsafe impl IsZero for $t {
+            #[inline]
+            fn is_zero(&self) -> bool {
+                $is_zero(*self)
+            }
+        }
+    };
+}
+
+impl_is_zero!(i16, |x| x == 0);
+impl_is_zero!(i32, |x| x == 0);
+impl_is_zero!(i64, |x| x == 0);
+impl_is_zero!(i128, |x| x == 0);
+impl_is_zero!(isize, |x| x == 0);
+
+impl_is_zero!(u16, |x| x == 0);
+impl_is_zero!(u32, |x| x == 0);
+impl_is_zero!(u64, |x| x == 0);
+impl_is_zero!(u128, |x| x == 0);
+impl_is_zero!(usize, |x| x == 0);
+
+impl_is_zero!(bool, |x| x == false);
+impl_is_zero!(char, |x| x == '\0');
+
+impl_is_zero!(f32, |x: f32| x.to_bits() == 0);
+impl_is_zero!(f64, |x: f64| x.to_bits() == 0);
+
+unsafe impl<T> IsZero for *const T {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        (*self).is_null()
+    }
+}
+
+unsafe impl<T> IsZero for *mut T {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        (*self).is_null()
+    }
+}
+
+// `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
+// For fat pointers, the bytes that would be the pointer metadata in the `Some`
+// variant are padding in the `None` variant, so ignoring them and
+// zero-initializing instead is ok.
+// `Option<&mut T>` never implements `Clone`, so there's no need for an impl of
+// `SpecFromElem`.
+
+unsafe impl<T: ?Sized> IsZero for Option<&T> {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.is_none()
+    }
+}
+
+unsafe impl<T: ?Sized> IsZero for Option<Box<T>> {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.is_none()
+    }
+}

library/alloc/src/vec/mod.rs

@@ -97,6 +97,10 @@ pub (crate) use self::into_iter::AsIntoIter;
 
 mod into_iter;
 
+use self::is_zero::IsZero;
+
+mod is_zero;
+
 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
 ///
 /// # Examples
@@ -2042,76 +2046,6 @@ impl<T: Clone + IsZero> SpecFromElem for T {
     }
 }
 
-#[rustc_specialization_trait]
-unsafe trait IsZero {
-    /// Whether this value is zero
-    fn is_zero(&self) -> bool;
-}
-
-macro_rules! impl_is_zero {
-    ($t:ty, $is_zero:expr) => {
-        unsafe impl IsZero for $t {
-            #[inline]
-            fn is_zero(&self) -> bool {
-                $is_zero(*self)
-            }
-        }
-    };
-}
-
-impl_is_zero!(i16, |x| x == 0);
-impl_is_zero!(i32, |x| x == 0);
-impl_is_zero!(i64, |x| x == 0);
-impl_is_zero!(i128, |x| x == 0);
-impl_is_zero!(isize, |x| x == 0);
-
-impl_is_zero!(u16, |x| x == 0);
-impl_is_zero!(u32, |x| x == 0);
-impl_is_zero!(u64, |x| x == 0);
-impl_is_zero!(u128, |x| x == 0);
-impl_is_zero!(usize, |x| x == 0);
-
-impl_is_zero!(bool, |x| x == false);
-impl_is_zero!(char, |x| x == '\0');
-
-impl_is_zero!(f32, |x: f32| x.to_bits() == 0);
-impl_is_zero!(f64, |x: f64| x.to_bits() == 0);
-
-unsafe impl<T> IsZero for *const T {
-    #[inline]
-    fn is_zero(&self) -> bool {
-        (*self).is_null()
-    }
-}
-
-unsafe impl<T> IsZero for *mut T {
-    #[inline]
-    fn is_zero(&self) -> bool {
-        (*self).is_null()
-    }
-}
-
-// `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
-// For fat pointers, the bytes that would be the pointer metadata in the `Some`
-// variant are padding in the `None` variant, so ignoring them and
-// zero-initializing instead is ok.
-// `Option<&mut T>` never implements `Clone`, so there's no need for an impl of
-// `SpecFromElem`.
-
-unsafe impl<T: ?Sized> IsZero for Option<&T> {
-    #[inline]
-    fn is_zero(&self) -> bool {
-        self.is_none()
-    }
-}
-
-unsafe impl<T: ?Sized> IsZero for Option<Box<T>> {
-    #[inline]
-    fn is_zero(&self) -> bool {
-        self.is_none()
-    }
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 // Common trait implementations for Vec
 ////////////////////////////////////////////////////////////////////////////////