Merge rust-bitcoin/rust-miniscript#492: DefiniteDescriptorKey: provide additional methods for converting to a DescriptorPublicKey

1477dbbb80523dde399a7cbaba25cbac54bf2816 DefiniteDescriptorKey: provide additional methods for converting to a DescriptorPublicKey (Andrew Poelstra)

Pull request description:

  Fixes #491

  I didn't provide a mutable version of this. I'm not sure if we want to support this or not; generally public keys should be immutable after creation.

ACKs for top commit:
  sanket1729:
    ACK 1477dbbb80523dde399a7cbaba25cbac54bf2816

Tree-SHA512: 8c06ac3b6c395c3805b8cbd958ce4f354025ee88b2915562662cb084216048c6543591c468112981e8afa72d89373a544965096227475f0c198af9194d826a7e

Author: heap-coder

src/descriptor/key.rs

@@ -1067,6 +1067,16 @@ impl DefiniteDescriptorKey {
     pub fn full_derivation_path(&self) -> Option<bip32::DerivationPath> {
         self.0.full_derivation_path()
     }
+
+    /// Reference to the underlying `DescriptorPublicKey`
+    pub fn as_descriptor_public_key(&self) -> &DescriptorPublicKey {
+        &self.0
+    }
+
+    /// Converts the definite key into a generic one
+    pub fn into_descriptor_public_key(self) -> DescriptorPublicKey {
+        self.0
+    }
 }
 
 impl FromStr for DefiniteDescriptorKey {
@@ -1134,6 +1144,12 @@ impl From<DefiniteDescriptorKey> for DescriptorPublicKey {
     }
 }
 
+impl Borrow<DescriptorPublicKey> for DefiniteDescriptorKey {
+    fn borrow(&self) -> &DescriptorPublicKey {
+        &self.0
+    }
+}
+
 #[cfg(test)]
 mod test {
     use core::str::FromStr;