num_traits::{Zero, One}

Author: Kestrer

macro/src/lib.rs

@@ -187,14 +187,21 @@ pub fn bounded_integer(input: proc_macro::TokenStream) -> proc_macro::TokenStrea
         [t] => panic!("named ({t})"),
     }
 
-    let zeroable = min_val
+    let zero = min_val
         .zip(max_val)
         .map(|(min, max)| (min..=max).contains(&Int::new(true, 0)));
-    if zeroable == Some(true) && zerocopy {
+    let one = min_val
+        .zip(max_val)
+        .map(|(min, max)| (min..=max).contains(&Int::new(true, 1)));
+    if zero == Some(true) && zerocopy {
         attrs.extend(quote!(#[derive(#crate_path::__private::zerocopy::FromZeros)]));
     }
-    let zeroable_token = match zeroable {
-        Some(true) => quote!(zeroable,),
+    let zero_token = match zero {
+        Some(true) => quote!(zero,),
+        Some(false) | None => quote!(),
+    };
+    let one_token = match one {
+        Some(true) => quote!(one,),
         Some(false) | None => quote!(),
     };
 
@@ -224,7 +231,7 @@ pub fn bounded_integer(input: proc_macro::TokenStream) -> proc_macro::TokenStrea
 
     let item = match variants {
         Some(variants) => quote!({ #variants }),
-        None if zeroable == Some(false) => quote!((::core::num::NonZero<#repr>);),
+        None if zero == Some(false) => quote!((::core::num::NonZero<#repr>);),
         None => quote!((#repr);),
     };
 
@@ -242,7 +249,8 @@ pub fn bounded_integer(input: proc_macro::TokenStream) -> proc_macro::TokenStrea
                 unsafe repr: #repr,
                 min: #min,
                 max: #max,
-                #zeroable_token
+                #zero_token
+                #one_token
             }
         }
         #vis use #module_name::#name;

src/lib.rs

@@ -103,6 +103,7 @@
 
 // TODO: propagate warning attributes to all items in the macro
 // TODO: TryFrom and TryInto
+// TODO: Test the `where` clause
 
 #[cfg(feature = "std")]
 extern crate std;

src/macro.rs

@@ -317,9 +317,13 @@ mod tests {
 
     #[test]
     fn zeroable() {
-        #[cfg(all(feature = "bytemuck1", feature = "zerocopy"))]
-        fn assert_zeroable<T: Default + bytemuck1::Zeroable + zerocopy::FromZeros>() {}
-        #[cfg(not(all(feature = "bytemuck1", feature = "zerocopy")))]
+        #[cfg(all(feature = "bytemuck1", feature = "zerocopy", feature = "num-traits02"))]
+        fn assert_zeroable<T>()
+        where
+            T: Default + bytemuck1::Zeroable + zerocopy::FromZeros + num_traits02::Zero,
+        {
+        }
+        #[cfg(not(all(feature = "bytemuck1", feature = "zerocopy", feature = "num-traits02")))]
         fn assert_zeroable<T: Default>() {}
         #[expect(unused)]
         trait NotZeroable<const N: usize> {}
@@ -328,13 +332,17 @@ mod tests {
         impl<T: bytemuck1::Zeroable> NotZeroable<1> for T {}
         #[cfg(feature = "zerocopy")]
         impl<T: zerocopy::FromZeros> NotZeroable<2> for T {}
+        #[cfg(feature = "num-traits02")]
+        impl<T: num_traits02::Zero> NotZeroable<3> for T {}
         macro_rules! not_zeroable {
             ($t:ty) => {
                 impl NotZeroable<0> for $t {}
                 #[cfg(feature = "bytemuck1")]
                 impl NotZeroable<1> for $t {}
                 #[cfg(feature = "zerocopy")]
                 impl NotZeroable<2> for $t {}
+                #[cfg(feature = "num-traits02")]
+                impl NotZeroable<3> for $t {}
             };
         }
 
@@ -357,6 +365,14 @@ mod tests {
         assert_ne!(size_of::<Option<E>>(), size_of::<E>());
     }
 
+    #[test]
+    #[cfg(feature = "num-traits02")]
+    fn one() {
+        fn assert_one<T: num_traits02::One>() {}
+        bounded_integer!(struct A(1, 1););
+        assert_one::<A>();
+    }
+
     #[test]
     #[cfg(feature = "zerocopy")]
     fn unaligned() {

src/unsafe_api.rs

@@ -7,7 +7,8 @@
 /// Takes in a `ty` and a `repr`. `ty` must be a type whose layout is identical to `repr`.
 ///
 /// `min` and `max` are const expressions giving the bounds of the type (inclusive).
-/// If `zeroable` is provided, various traits like [`Default`] will be implemented.
+/// If `zero` is provided, various traits like [`Default`] will be implemented;
+/// if `one` is provided, `num_traits::One` will be implemented.
 ///
 /// # Safety
 ///
@@ -25,7 +26,8 @@
 ///     unsafe repr: u8,
 ///     min: 0,
 ///     max: 37,
-///     zeroable,
+///     zero,
+///     one,
 /// }
 ///
 /// assert_eq!(MyInteger::new(0).unwrap(), 0);
@@ -52,15 +54,17 @@ macro_rules! unsafe_api {
         unsafe repr: $repr:tt,
         min: $min:expr,
         max: $max:expr,
-        $(zeroable $([$($_:tt)* $zeroable:tt])?,)?
+        $(zero $([$($_:tt)* $zero:tt])?,)?
+        $(one $([$($__:tt)* $one:tt])?,)?
     ) => {
         $crate::__unsafe_api_internal! {
             @repr $repr,
             [$($($generics)*)?] $ty where { $($($where)*)? },
             ([$($($generics)*)?] where $($($where)*)?),
             min: $min,
             max: $max,
-            $(zeroable, $($zeroable)?)?
+            $(zero, $($zero)?)?
+            $(one, $($one)?)?
         }
     };
 }
@@ -80,7 +84,8 @@ macro_rules! __unsafe_api_internal {
         $generics_single_token:tt,
         min: $min:expr,
         max: $max:expr,
-        $(zeroable $([$zeroable:tt])?,)?
+        $(zero $([$zero:tt])?,)?
+        $(one $([$one:tt])?,)?
     ) => { const _: () = {
         // The presence of these imports is somewhat unhygienic: it means users cannot name their
         // type any of these things. This can always be changed if the need arises.
@@ -700,12 +705,23 @@ macro_rules! __unsafe_api_internal {
 
         // === Default ===
 
-        #[cfg(not(all($($($zeroable)? false)?)))]
+        #[cfg(not(all($($($zero)? false)?)))]
         #[automatically_derived]
         impl<$($generics)*> Default for $ty where $($where)* {
             fn default() -> Self {
                 const {
-                    Self::new(0).expect("used `zeroable` on a type whose range does not include zero")
+                    Self::new(0).expect("used `zero` on a type whose range does not include zero")
+                }
+            }
+        }
+
+        // Use a function to force post-mono errors even if `num-traits02` is disabled.
+        #[cfg(not(all($($($one)? false)?)))]
+        impl<$($generics)*> $ty where $($where)* {
+            #[allow(unused)]
+            fn one() -> Self {
+                const {
+                    Self::new(1).expect("used `one` on a type whose range does not include one")
                 }
             }
         }
@@ -1013,7 +1029,7 @@ macro_rules! __unsafe_api_internal {
             #[automatically_derived]
             unsafe impl<$($generics)*> bytemuck1::NoUninit for $ty {}
 
-            #[cfg(not(all($($(if $zeroable)? false)?)))]
+            #[cfg(not(all($($(if $zero)? false)?)))]
             #[automatically_derived]
             unsafe impl<$($generics)*> bytemuck1::Zeroable for $ty {}
         }
@@ -1241,7 +1257,24 @@ macro_rules! __unsafe_api_internal {
                 }
             }
 
-            // TODO: implement `Zero`/`One`?
+            #[cfg(not(all($($($zero)? false)?)))]
+            #[automatically_derived]
+            impl<$($generics)*> num_traits02::Zero for $ty {
+                fn zero() -> Self {
+                    Self::default()
+                }
+                fn is_zero(&self) -> bool {
+                    self.get() == 0
+                }
+            }
+
+            #[cfg(not(all($($($one)? false)?)))]
+            #[automatically_derived]
+            impl<$($generics)*> num_traits02::One for $ty {
+                fn one() -> Self {
+                    Self::one()
+                }
+            }
         }
 
         // === Serde ===
@@ -1530,7 +1563,7 @@ mod tests {
             },
             min: -5,
             max: 5,
-            zeroable,
+            zero,
         }
     }
 }

ui/bad_range.rs

@@ -1,4 +1,3 @@
-#![cfg_attr(feature = "step_trait", feature(step_trait))]
 fn main() {
     #![expect(unused)]
     let _ = <bounded_integer::BoundedUsize<5, 4>>::MIN;

ui/bad_range.stderr

@@ -13,39 +13,39 @@ error[E0080]: evaluation panicked: range minimum should be less than maximum
   = note: this error originates in the macro `$crate::__unsafe_api_internal` which comes from the expansion of the macro `define_bounded_integers` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered
- --> ui/bad_range.rs:4:13
+ --> ui/bad_range.rs:3:13
   |
-4 |     let _ = <bounded_integer::BoundedUsize<5, 4>>::MIN;
+3 |     let _ = <bounded_integer::BoundedUsize<5, 4>>::MIN;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0080]: evaluation panicked: range minimum should be less than maximum
- --> ui/bad_range.rs:5:5
+ --> ui/bad_range.rs:4:5
   |
-5 |     bounded_integer::bounded_integer!(struct X(5, 4););
+4 |     bounded_integer::bounded_integer!(struct X(5, 4););
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation of `main::__bounded_integer_private_X::_::<impl main::__bounded_integer_private_X::X>::MIN` failed here
   |
   = note: this error originates in the macro `$crate::__unsafe_api_internal` which comes from the expansion of the macro `bounded_integer::bounded_integer` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered
- --> ui/bad_range.rs:5:5
+ --> ui/bad_range.rs:4:5
   |
-5 |     bounded_integer::bounded_integer!(struct X(5, 4););
+4 |     bounded_integer::bounded_integer!(struct X(5, 4););
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this note originates in the macro `$crate::__unsafe_api_internal` which comes from the expansion of the macro `bounded_integer::bounded_integer` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation panicked: range minimum should be less than maximum
- --> ui/bad_range.rs:5:5
+ --> ui/bad_range.rs:4:5
   |
-5 |     bounded_integer::bounded_integer!(struct X(5, 4););
+4 |     bounded_integer::bounded_integer!(struct X(5, 4););
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation of `main::__bounded_integer_private_X::_::<impl main::__bounded_integer_private_X::X>::MAX` failed here
   |
   = note: this error originates in the macro `$crate::__unsafe_api_internal` which comes from the expansion of the macro `bounded_integer::bounded_integer` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered
- --> ui/bad_range.rs:5:5
+ --> ui/bad_range.rs:4:5
   |
-5 |     bounded_integer::bounded_integer!(struct X(5, 4););
+4 |     bounded_integer::bounded_integer!(struct X(5, 4););
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this note originates in the macro `$crate::__unsafe_api_internal` which comes from the expansion of the macro `bounded_integer::bounded_integer` (in Nightly builds, run with -Z macro-backtrace for more info)

ui/const_new.rs

@@ -1,4 +1,3 @@
-#![cfg_attr(feature = "step_trait", feature(step_trait))]
 fn main() {
     let _ = <bounded_integer::BoundedUsize<0, 5>>::const_new::<6>();
 }

ui/const_new.stderr

@@ -27,7 +27,7 @@ note: erroneous constant encountered
    = note: this note originates in the macro `$crate::__unsafe_api_internal` which comes from the expansion of the macro `define_bounded_integers` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: the above error was encountered while instantiating `fn bounded_integer::types::_::<impl bounded_integer::BoundedUsize<0, 5>>::const_new::<6>`
- --> ui/const_new.rs:3:13
+ --> ui/const_new.rs:2:13
   |
-3 |     let _ = <bounded_integer::BoundedUsize<0, 5>>::const_new::<6>();
+2 |     let _ = <bounded_integer::BoundedUsize<0, 5>>::const_new::<6>();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

ui/macro.rs

@@ -1,5 +1,3 @@
-#![cfg_attr(feature = "step_trait", feature(step_trait))]
-
 use bounded_integer::bounded_integer;
 
 bounded_integer! {