Add ConstBounded trait

Add test const_bounded_impl

src/bounds.rs

@@ -7,13 +7,29 @@ use core::{u16, u32, u64, u8, usize};
 
 /// Numbers which have upper and lower bounds
 pub trait Bounded {
-    // FIXME (#5527): These should be associated constants
     /// returns the smallest finite number this type can represent
     fn min_value() -> Self;
     /// returns the largest finite number this type can represent
     fn max_value() -> Self;
 }
 
+/// Supplimentary trait for [`Bounded`](trait.Bounded.html) types which can be
+/// expressed as compile-time constants.
+///
+/// This is implemented for all primitive types, and should be implemented
+/// wherever possible. Implementors must ensure that `ConstBounded::MIN_VALUE`
+/// and `ConstBounded::MAX_VALUE` are the same values produced by 
+/// [`Bounded::min_value()`](trait.Bounded.html#tymethod.min_value) and
+/// [`Bounded::max_value()`](trait.Bounded.html#tymethod.max_value)
+/// respectively.
+#[cfg(has_associated_consts)]
+pub trait ConstBounded: Bounded {
+    /// The smallest finite number this type can represent
+    const MIN_VALUE: Self;
+    /// The largest finite number this type can represent
+    const MAX_VALUE: Self;
+}
+
 macro_rules! bounded_impl {
     ($t:ty, $min:expr, $max:expr) => {
         impl Bounded for $t {
@@ -30,21 +46,39 @@ macro_rules! bounded_impl {
     };
 }
 
-bounded_impl!(usize, usize::MIN, usize::MAX);
-bounded_impl!(u8, u8::MIN, u8::MAX);
-bounded_impl!(u16, u16::MIN, u16::MAX);
-bounded_impl!(u32, u32::MIN, u32::MAX);
-bounded_impl!(u64, u64::MIN, u64::MAX);
-#[cfg(has_i128)]
-bounded_impl!(u128, u128::MIN, u128::MAX);
+#[cfg(has_associated_consts)]
+macro_rules! bounded_const_impl {
+    ($t:ty, $min:expr, $max:expr) => {
+        bounded_impl!($t, $min, $max);
+        impl ConstBounded for $t {
+            const MIN_VALUE: $t = $min;
+            const MAX_VALUE: $t = $max;
+        }
+    }
+}
+#[cfg(not(has_associated_consts))]
+macro_rules! bounded_const_impl {
+    ($t:ty, $min:expr, $max:expr) => { bounded_impl!($t, $min, $max); };
+}
 
-bounded_impl!(isize, isize::MIN, isize::MAX);
-bounded_impl!(i8, i8::MIN, i8::MAX);
-bounded_impl!(i16, i16::MIN, i16::MAX);
-bounded_impl!(i32, i32::MIN, i32::MAX);
-bounded_impl!(i64, i64::MIN, i64::MAX);
+bounded_const_impl!(usize, usize::MIN, usize::MAX);
+bounded_const_impl!(u8, u8::MIN, u8::MAX);
+bounded_const_impl!(u16, u16::MIN, u16::MAX);
+bounded_const_impl!(u32, u32::MIN, u32::MAX);
+bounded_const_impl!(u64, u64::MIN, u64::MAX);
 #[cfg(has_i128)]
-bounded_impl!(i128, i128::MIN, i128::MAX);
+bounded_const_impl!(u128, u128::MIN, u128::MAX);
+
+bounded_const_impl!(isize, isize::MIN, isize::MAX);
+bounded_const_impl!(i8, i8::MIN, i8::MAX);
+bounded_const_impl!(i16, i16::MIN, i16::MAX);
+bounded_const_impl!(i32, i32::MIN, i32::MAX);
+bounded_const_impl!(i64, i64::MIN, i64::MAX);
+#[cfg(has_i128)]
+bounded_const_impl!(i128, i128::MIN, i128::MAX);
+
+bounded_const_impl!(f32, f32::MIN, f32::MAX);
+bounded_const_impl!(f64, f64::MIN, f64::MAX);
 
 impl<T: Bounded> Bounded for Wrapping<T> {
     fn min_value() -> Self {
@@ -54,8 +88,11 @@ impl<T: Bounded> Bounded for Wrapping<T> {
         Wrapping(T::max_value())
     }
 }
-
-bounded_impl!(f32, f32::MIN, f32::MAX);
+#[cfg(has_associated_consts)]
+impl<T: ConstBounded> ConstBounded for Wrapping<T> {
+    const MIN_VALUE: Self = Wrapping(T::MIN_VALUE);
+    const MAX_VALUE: Self = Wrapping(T::MAX_VALUE);
+}
 
 macro_rules! for_each_tuple_ {
     ( $m:ident !! ) => (
@@ -86,9 +123,19 @@ macro_rules! bounded_tuple {
         }
     );
 }
-
 for_each_tuple!(bounded_tuple);
-bounded_impl!(f64, f64::MIN, f64::MAX);
+
+#[cfg(has_associated_consts)]
+macro_rules! bounded_const_tuple {
+    ( $($name:ident)* ) => (
+        impl<$($name: ConstBounded,)*> ConstBounded for ($($name,)*) {
+            const MIN_VALUE: Self = ($($name::MIN_VALUE,)*);
+            const MAX_VALUE: Self = ($($name::MAX_VALUE,)*);
+        }
+    );
+}
+#[cfg(has_associated_consts)]
+for_each_tuple!(bounded_const_tuple);
 
 #[test]
 fn wrapping_bounded() {
@@ -125,3 +172,27 @@ fn wrapping_is_bounded() {
     require_bounded(&Wrapping(42_u32));
     require_bounded(&Wrapping(-42));
 }
+
+#[test]
+#[cfg(has_associated_consts)]
+fn const_bounded_impl() {
+    macro_rules! test_traits_match {
+        ($($t:ty),+) => { $(
+            assert_eq!(
+                <$t as Bounded>::min_value(), 
+                <$t as ConstBounded>::MIN_VALUE,
+            );
+            assert_eq!(
+                <$t as Bounded>::max_value(), 
+                <$t as ConstBounded>::MAX_VALUE,
+            );
+        )+};
+    }
+    test_traits_match!(
+        u8, u16, u32, u64, usize, 
+        i8, i16, i32, i64, isize,
+        f32, f64,
+        Wrapping<usize>, Wrapping<isize>,
+        (u8, i32, f32, Wrapping<u8>, (i8, ((), u16), Wrapping<i16>, f64))
+    );
+}

src/lib.rs

@@ -26,6 +26,8 @@ use core::ops::{Add, Div, Mul, Rem, Sub};
 use core::ops::{AddAssign, DivAssign, MulAssign, RemAssign, SubAssign};
 
 pub use bounds::Bounded;
+#[cfg(has_associated_consts)]
+pub use bounds::ConstBounded;
 #[cfg(feature = "std")]
 pub use float::Float;
 pub use float::FloatConst;