Use more informative type names in Extension trait.

zcash_extensions/src/consensus/transparent.rs

@@ -1,7 +1,7 @@
 //! Consensus logic for Transparent Zcash Extensions.
 
 use std::convert::TryFrom;
-use zcash_primitives::consensus::NetworkUpgrade;
+use zcash_primitives::consensus::{BlockHeight, NetworkUpgrade};
 use zcash_primitives::extensions::transparent::{Error, Extension, Precondition, Witness};
 use zcash_primitives::transaction::{components::TzeOut, Transaction};
 
@@ -41,12 +41,12 @@ impl From<ExtensionId> for u32 {
 /// an assigned extension type ID. This type may be modified in the future if
 /// additional context information is required by newly integrated TZEs.
 pub struct Context<'a> {
-    pub height: i32,
+    pub height: BlockHeight,
     pub tx: &'a Transaction,
 }
 
 impl<'a> Context<'a> {
-    pub fn new(height: i32, tx: &'a Transaction) -> Self {
+    pub fn new(height: BlockHeight, tx: &'a Transaction) -> Self {
         Context { height, tx }
     }
 }

zcash_extensions/src/transparent/demo.rs

@@ -249,8 +249,8 @@ pub trait Context {
 pub struct Program;
 
 impl<C: Context> Extension<C> for Program {
-    type P = Precondition;
-    type W = Witness;
+    type Precondition = Precondition;
+    type Witness = Witness;
     type Error = Error;
 
     /// Runs the program against the given precondition, witness, and context.

zcash_primitives/src/extensions/transparent.rs

@@ -116,12 +116,12 @@ pub trait Extension<C> {
     /// Extension-specific precondition type. The extension will need to implement
     /// [`FromPayload<Error = Self::Error>`] for this type in order for their
     /// extension to be eligible for integration into consensus rules.
-    type P;
+    type Precondition;
 
     /// Extension-specific witness type. The extension will need to implement
     /// [`FromPayload<Error = Self::Error>`] for this type in order for their
     /// extension to be eligible for integration into consensus rules.
-    type W;
+    type Witness;
 
     /// Extension-specific error type. This should encompass both parsing and verification errors.
     type Error;
@@ -131,8 +131,8 @@ pub trait Extension<C> {
     /// precondition, and an error in any other case.
     fn verify_inner(
         &self,
-        precondition: &Self::P,
-        witness: &Self::W,
+        precondition: &Self::Precondition,
+        witness: &Self::Witness,
         context: &C,
     ) -> Result<(), Self::Error>;
 
@@ -146,12 +146,12 @@ pub trait Extension<C> {
         context: &C,
     ) -> Result<(), Self::Error>
     where
-        Self::P: FromPayload<Error = Self::Error>,
-        Self::W: FromPayload<Error = Self::Error>,
+        Self::Precondition: FromPayload<Error = Self::Error>,
+        Self::Witness: FromPayload<Error = Self::Error>,
     {
         self.verify_inner(
-            &Self::P::from_payload(precondition.mode, &precondition.payload)?,
-            &Self::W::from_payload(witness.mode, &witness.payload)?,
+            &Self::Precondition::from_payload(precondition.mode, &precondition.payload)?,
+            &Self::Witness::from_payload(witness.mode, &witness.payload)?,
             &context,
         )
     }