Remove unsigned_script_sig from DescriptorTrait

In preparation for removing the `DescriptorTrait` move the
`unsigned_script_sig` trait methods onto each individual descriptor as
required (`Sh` only). All the other trait method implementations just
return `Script::new()`, just call `new` directly from the implantation
of `unsigned_script_sig` on `Descriptor`.

Author: heap-coder

src/descriptor/bare.rs

@@ -138,13 +138,6 @@ where
 }
 
 impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Bare<Pk> {
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey,
-    {
-        Script::new()
-    }
-
     fn explicit_script(&self) -> Result<Script, Error>
     where
         Pk: ToPublicKey,
@@ -326,13 +319,6 @@ where
 }
 
 impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Pkh<Pk> {
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey,
-    {
-        Script::new()
-    }
-
     fn explicit_script(&self) -> Result<Script, Error>
     where
         Pk: ToPublicKey,

src/descriptor/mod.rs

@@ -76,18 +76,6 @@ pub type KeyMap = HashMap<DescriptorPublicKey, DescriptorSecretKey>;
 // because of traits cannot know underlying generic of Self.
 // Thus, we must implement additional trait for translate function
 pub trait DescriptorTrait<Pk: MiniscriptKey> {
-    /// Computes the scriptSig that will be in place for an unsigned
-    /// input spending an output with this descriptor. For pre-segwit
-    /// descriptors, which use the scriptSig for signatures, this
-    /// returns the empty script.
-    ///
-    /// This is used in Segwit transactions to produce an unsigned
-    /// transaction whose txid will not change during signing (since
-    /// only the witness data will change).
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey;
-
     /// Computes the "witness script" of the descriptor, i.e. the underlying
     /// script before any hashing is done. For `Bare`, `Pkh` and `Wpkh` this
     /// is the scriptPubkey; for `ShWpkh` and `Sh` this is the redeemScript;
@@ -423,6 +411,24 @@ impl<Pk: MiniscriptKey + ToPublicKey> Descriptor<Pk> {
             Descriptor::Tr(ref tr) => tr.script_pubkey(),
         }
     }
+
+    /// Computes the scriptSig that will be in place for an unsigned input
+    /// spending an output with this descriptor. For pre-segwit descriptors,
+    /// which use the scriptSig for signatures, this returns the empty script.
+    ///
+    /// This is used in Segwit transactions to produce an unsigned transaction
+    /// whose txid will not change during signing (since only the witness data
+    /// will change).
+    pub fn unsigned_script_sig(&self) -> Script {
+        match *self {
+            Descriptor::Bare(_) => Script::new(),
+            Descriptor::Pkh(_) => Script::new(),
+            Descriptor::Wpkh(_) => Script::new(),
+            Descriptor::Wsh(_) => Script::new(),
+            Descriptor::Sh(ref sh) => sh.unsigned_script_sig(),
+            Descriptor::Tr(_) => Script::new(),
+        }
+    }
 }
 
 impl<P, Q> TranslatePk<P, Q> for Descriptor<P>
@@ -456,28 +462,6 @@ where
 }
 
 impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Descriptor<Pk> {
-    /// Computes the scriptSig that will be in place for an unsigned
-    /// input spending an output with this descriptor. For pre-segwit
-    /// descriptors, which use the scriptSig for signatures, this
-    /// returns the empty script.
-    ///
-    /// This is used in Segwit transactions to produce an unsigned
-    /// transaction whose txid will not change during signing (since
-    /// only the witness data will change).
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey,
-    {
-        match *self {
-            Descriptor::Bare(ref bare) => bare.unsigned_script_sig(),
-            Descriptor::Pkh(ref pkh) => pkh.unsigned_script_sig(),
-            Descriptor::Wpkh(ref wpkh) => wpkh.unsigned_script_sig(),
-            Descriptor::Wsh(ref wsh) => wsh.unsigned_script_sig(),
-            Descriptor::Sh(ref sh) => sh.unsigned_script_sig(),
-            Descriptor::Tr(ref tr) => tr.unsigned_script_sig(),
-        }
-    }
-
     /// Computes the "witness script" of the descriptor, i.e. the underlying
     /// script before any hashing is done. For `Bare`, `Pkh` and `Wpkh` this
     /// is the scriptPubkey; for `ShWpkh` and `Sh` this is the redeemScript;

src/descriptor/segwitv0.rs

@@ -196,13 +196,6 @@ where
 }
 
 impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Wsh<Pk> {
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey,
-    {
-        Script::new()
-    }
-
     fn explicit_script(&self) -> Result<Script, Error>
     where
         Pk: ToPublicKey,
@@ -438,13 +431,6 @@ where
 }
 
 impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Wpkh<Pk> {
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey,
-    {
-        Script::new()
-    }
-
     fn explicit_script(&self) -> Result<Script, Error>
     where
         Pk: ToPublicKey,

src/descriptor/sh.rs

@@ -272,13 +272,15 @@ impl<Pk: MiniscriptKey + ToPublicKey> Sh<Pk> {
             ShInner::Ms(ref ms) => ms.encode(),
         }
     }
-}
 
-impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Sh<Pk> {
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey,
-    {
+    /// Computes the scriptSig that will be in place for an unsigned input
+    /// spending an output with this descriptor. For pre-segwit descriptors,
+    /// which use the scriptSig for signatures, this returns the empty script.
+    ///
+    /// This is used in Segwit transactions to produce an unsigned transaction
+    /// whose txid will not change during signing (since only the witness data
+    /// will change).
+    pub fn unsigned_script_sig(&self) -> Script {
         match self.inner {
             ShInner::Wsh(ref wsh) => {
                 // wsh explicit must contain exactly 1 element
@@ -296,7 +298,9 @@ impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Sh<Pk> {
             ShInner::SortedMulti(..) | ShInner::Ms(..) => Script::new(),
         }
     }
+}
 
+impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Sh<Pk> {
     fn explicit_script(&self) -> Result<Script, Error>
     where
         Pk: ToPublicKey,

src/descriptor/tr.rs

@@ -554,13 +554,6 @@ impl<Pk: MiniscriptKey> Liftable<Pk> for Tr<Pk> {
 }
 
 impl<Pk: MiniscriptKey> DescriptorTrait<Pk> for Tr<Pk> {
-    fn unsigned_script_sig(&self) -> Script
-    where
-        Pk: ToPublicKey,
-    {
-        Script::new()
-    }
-
     fn explicit_script(&self) -> Result<Script, Error>
     where
         Pk: ToPublicKey,