Implement alloc::vec::IsZero for Option<$NUM> types

Author: clubby789

alloc/src/lib.rs

@@ -106,6 +106,7 @@
 #![feature(const_size_of_val)]
 #![feature(const_align_of_val)]
 #![feature(const_ptr_read)]
+#![feature(const_maybe_uninit_zeroed)]
 #![feature(const_maybe_uninit_write)]
 #![feature(const_maybe_uninit_as_mut_ptr)]
 #![feature(const_refs_to_cell)]

alloc/src/vec/is_zero.rs

@@ -147,6 +147,23 @@ impl_is_zero_option_of_nonzero!(
     NonZeroIsize,
 );
 
+macro_rules! impl_is_zero_option_of_num {
+    ($($t:ty,)+) => {$(
+        unsafe impl IsZero for Option<$t> {
+            #[inline]
+            fn is_zero(&self) -> bool {
+                const {
+                    let none: Self = unsafe { core::mem::MaybeUninit::zeroed().assume_init() };
+                    assert!(none.is_none());
+                }
+                self.is_none()
+            }
+        }
+    )+};
+}
+
+impl_is_zero_option_of_num!(u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, usize, isize,);
+
 unsafe impl<T: IsZero> IsZero for Wrapping<T> {
     #[inline]
     fn is_zero(&self) -> bool {