add Expected trait to utils; use (already transitive) num-traits.

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/utils/math/expected.rs

@@ -0,0 +1,52 @@
+use num_traits::ops::checked::{CheckedAdd, CheckedDiv, CheckedMul, CheckedRem, CheckedSub};
+
+use crate::expected;
+
+pub trait Expected {
+	#[inline]
+	#[must_use]
+	fn expected_add(self, rhs: Self) -> Self
+	where
+		Self: CheckedAdd + Sized,
+	{
+		expected!(self + rhs)
+	}
+
+	#[inline]
+	#[must_use]
+	fn expected_sub(self, rhs: Self) -> Self
+	where
+		Self: CheckedSub + Sized,
+	{
+		expected!(self - rhs)
+	}
+
+	#[inline]
+	#[must_use]
+	fn expected_mul(self, rhs: Self) -> Self
+	where
+		Self: CheckedMul + Sized,
+	{
+		expected!(self * rhs)
+	}
+
+	#[inline]
+	#[must_use]
+	fn expected_div(self, rhs: Self) -> Self
+	where
+		Self: CheckedDiv + Sized,
+	{
+		expected!(self / rhs)
+	}
+
+	#[inline]
+	#[must_use]
+	fn expected_rem(self, rhs: Self) -> Self
+	where
+		Self: CheckedRem + Sized,
+	{
+		expected!(self % rhs)
+	}
+}
+
+impl<T> Expected for T {}