rust: pin-init: extend `impl_zeroable_option` macro to handle generics

Improve impl_zeroable_option macro to handle generic impls for types
like `&T`, `&mut T`, `NonNull<T>`, and others (for which `Option<T>`
is guaranteed to be zeroable) with similar approach to
`impl_zeroable`.

Also, update old declarations to use generics e.g. `NonZeroU8` to
`NonZero<u8>`.

Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260428-pin-init-sync-v1-4-07f9bd3859fb@garyguo.net
Signed-off-by: Gary Guo <gary@garyguo.net>

diff --git a/rust/pin-init/src/lib.rs b/rust/pin-init/src/lib.rs
index e34c9bdb88c39ea5d28de29846208b9337a00f84..9b76cf5597c62bffedf64d9564c492633286a342 100644 (file)
--- a/rust/pin-init/src/lib.rs
+++ b/rust/pin-init/src/lib.rs
@@ -1633,16 +1633,6 @@ pub unsafe trait ZeroableOption {}
 // SAFETY: by the safety requirement of `ZeroableOption`, this is valid.
 unsafe impl<T: ZeroableOption> Zeroable for Option<T> {}
 
-// SAFETY: `Option<&T>` is part of the option layout optimization guarantee:
-// <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
-unsafe impl<T> ZeroableOption for &T {}
-// SAFETY: `Option<&mut T>` is part of the option layout optimization guarantee:
-// <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
-unsafe impl<T> ZeroableOption for &mut T {}
-// SAFETY: `Option<NonNull<T>>` is part of the option layout optimization guarantee:
-// <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
-unsafe impl<T> ZeroableOption for NonNull<T> {}
-
 macro_rules! impl_fn_zeroable_option {
     ([$($abi:literal),* $(,)?] $args:tt) => {
         $(impl_fn_zeroable_option!({extern $abi} $args);)*
@@ -1669,17 +1659,26 @@ macro_rules! impl_fn_zeroable_option {
 impl_fn_zeroable_option!(["Rust", "C"] { A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U });
 
 macro_rules! impl_zeroable_option {
-    ($($int:ty),* $(,)?) => {
-        // SAFETY: Safety comment written in the macro invocation.
-        $(unsafe impl ZeroableOption for $int {})*
+    ($($({$($generics:tt)*})? $t:ty, )*) => {
+        // SAFETY: Safety comments written in the macro invocation.
+        $(unsafe impl$($($generics)*)? ZeroableOption for $t {})*
     };
 }
 
 impl_zeroable_option! {
+    // SAFETY: `Option<&T>` is part of the option layout optimization guarantee:
+    // <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
+    {<T: ?Sized>} &T,
+    // SAFETY: `Option<&mut T>` is part of the option layout optimization guarantee:
+    // <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
+    {<T: ?Sized>} &mut T,
+    // SAFETY: `Option<NonNull<T>>` is part of the option layout optimization guarantee:
+    // <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
+    {<T: ?Sized>} NonNull<T>,
     // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee:
     // <https://doc.rust-lang.org/stable/std/option/index.html#representation>).
-    NonZeroU8, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU128, NonZeroUsize,
-    NonZeroI8, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI128, NonZeroIsize,
+    NonZero<u8>, NonZero<u16>, NonZero<u32>, NonZero<u64>, NonZero<u128>, NonZero<usize>,
+    NonZero<i8>, NonZero<i16>, NonZero<i32>, NonZero<i64>, NonZero<i128>, NonZero<isize>,
 }
 
 /// This trait allows creating an instance of `Self` which contains exactly one