Merge rust-bitcoin#3403: Refine Sequence and Version Arbitrary …

…impls

9d98727 Refine Sequence and Version Arbitrary impls (Shing Him Ng)

Pull request description:

  Refine `Sequence` and `Version` `Arbitrary` impls with an equal weighting for special cases and the arbitrary case

  Idea originally posted here: rust-bitcoin#3363 (comment)

ACKs for top commit:
  tcharding:
    ACK 9d98727
  apoelstra:
    ACK 9d98727 successfully ran local tests

Tree-SHA512: 3274e4423515009187abc5d7e8dd0390b2fe4295c674ae4d784981fa2ac698f63ee69453ecbb9d6d36d6ff421753b38f7148fa41b11bc5460673a603ccfeb8c5

primitives/src/sequence.rs

@@ -244,7 +244,27 @@ units::impl_parse_str_from_int_infallible!(Sequence, u32, from_consensus);
 #[cfg(feature = "arbitrary")]
 impl<'a> Arbitrary<'a> for Sequence {
     fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
-        let s = u32::arbitrary(u)?;
-        Ok(Sequence(s))
+        let mut choice_range = 4;
+        if cfg!(feature = "alloc") {
+            choice_range = 8;
+        }
+
+        // Equally weight the cases of meaningful sequence numbers
+        let choice = u.int_in_range(0..=choice_range)?;
+        match choice {
+            0 => Ok(Sequence::MAX),
+            1 => Ok(Sequence::ZERO),
+            2 => Ok(Sequence::MIN_NO_RBF),
+            3 => Ok(Sequence::ENABLE_RBF_NO_LOCKTIME),
+            #[cfg(feature = "alloc")]
+            4 => Ok(Sequence::from_consensus(relative::Height::MIN.to_consensus_u32())),
+            #[cfg(feature = "alloc")]
+            5 => Ok(Sequence::from_consensus(relative::Height::MAX.to_consensus_u32())),
+            #[cfg(feature = "alloc")]
+            6 => Ok(Sequence::from_consensus(relative::Time::MIN.to_consensus_u32())),
+            #[cfg(feature = "alloc")]
+            7 => Ok(Sequence::from_consensus(relative::Time::MAX.to_consensus_u32())),
+            _ => Ok(Sequence(u.arbitrary()?))
+        }
     }
 }

primitives/src/transaction.rs

@@ -76,8 +76,13 @@ impl fmt::Display for Version {
 #[cfg(feature = "arbitrary")]
 impl<'a> Arbitrary<'a> for Version {
     fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
-        let v = i32::arbitrary(u)?;
-        Ok(Version(v))
+        // Equally weight the case of normal version numbers
+        let choice = u.int_in_range(0..=2)?;
+        match choice {
+            0 => Ok(Version::ONE),
+            1 => Ok(Version::TWO),
+            _ => Ok(Version(u.arbitrary()?))
+        }
     }
 }