Add ExpectInto numerological conversion trait. (#357)

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

src/core/utils/math/expect_into.rs

@@ -0,0 +1,12 @@
+pub trait ExpectInto {
+	#[inline]
+	#[must_use]
+	fn expect_into<Dst: TryFrom<Self>>(self) -> Dst
+	where
+		Self: Sized,
+	{
+		super::expect_into::<Dst, Self>(self)
+	}
+}
+
+impl<T> ExpectInto for T {}