Merge #666: Manually implement is_uncompressed for BitcoinKey

52198dd Manually implement is_uncompressed for BitcoinKey (Tobin C. Harding)

Pull request description:

  The `interpreter::BitcoinKey` uses the default implementation of `MiniscriptKey`, which means `is_uncompressed` returns `false`. However if the full key is a `bitcoin::PublicKey` it may be compressed.

  Manually implement `MiniscriptKey::is_uncompressed` for `BitcoinKey` and return the compressedness of the inner full key.

  Originally done, and discussed, in #620.

ACKs for top commit:
  apoelstra:
    ACK 52198dd

Tree-SHA512: 59f514d24120cfc452e60c361f851280b0515e4b63eb5d2a94d84e39821e6c80f3af07eee5fc5f80bd7198d2e09c6e4465f6f6ef3e8f38dba87ef77a2e1a3b9a

src/interpreter/mod.rs

@@ -123,6 +123,13 @@ impl MiniscriptKey for BitcoinKey {
     type Hash256 = hash256::Hash;
     type Ripemd160 = ripemd160::Hash;
     type Hash160 = hash160::Hash;
+
+    fn is_uncompressed(&self) -> bool {
+        match *self {
+            BitcoinKey::Fullkey(pk) => !pk.compressed,
+            BitcoinKey::XOnlyPublicKey(_) => false,
+        }
+    }
 }
 
 impl<'txin> Interpreter<'txin> {