Finish conversion from u64 to SemVer and add test

src/semver.rs

@@ -65,7 +65,21 @@ impl TryFrom<u64> for SemVer {
     type Error = Error;
 
     fn try_from(value: u64) -> Result<Self, Self::Error> {
-        todo!()
+        let mut mask: u64 = 0o7777 << 52;
+        let major = (value & mask) >> 52;
+        mask = 0o7777 << 40;
+        let minor = (value & mask) >> 40;
+        mask = 0o7777 << 28;
+        let patch = (value & mask) >> 28;
+        mask = 0o37777;
+        let p = u16::try_from(value & mask)?;
+        let pre: PreRelease = p.try_into()?;
+        Ok(Self {
+            major: major.try_into()?,
+            minor: minor.try_into()?,
+            patch: patch.try_into()?,
+            pre,
+        })
     }
 }
 
@@ -142,6 +156,17 @@ mod tests {
         assert_eq!(s.to_string(), "2.1.14_beta2");
     }
 
+    #[test]
+    fn to_from_u64() {
+        let sem = SemVer {
+            major: 1,
+            minor: 0,
+            patch: 11,
+            pre: PreRelease::Beta(Some(NonZeroU16::new(2).unwrap())),
+        };
+        assert_eq!(SemVer::try_from(u64::from(sem)).unwrap(), sem);
+    }
+
     #[test]
     fn eq() {
         assert_eq!(