Add more docs, improve conversion u8 Felt and make verify_proof gener…

…ic over the hasher

src/trie/merkle_tree.rs

@@ -7,7 +7,7 @@ use bitvec::{
 };
 use derive_more::Constructor;
 use mp_felt::Felt252Wrapper;
-use mp_hashers::{pedersen::PedersenHasher, HasherT};
+use mp_hashers::HasherT;
 use parity_scale_codec::{Decode, Encode, Error, Input, Output};
 use std::{collections::HashMap, mem};
 
@@ -120,7 +120,7 @@ fn test_shared_path_encode_decode() {
 }
 /// A node used in proof generated by the trie.
 ///
-/// See pathfinders merkle-tree crate for more information.
+/// Each node hold only the minimum of data that need to be known for the proof: the child hashes (and path for edge node)
 #[derive(Debug, Clone, PartialEq)]
 pub enum ProofNode {
     Binary {
@@ -140,12 +140,10 @@ impl ProofNode {
             ProofNode::Edge { child, path } => {
                 let mut bytes = [0u8; 32];
                 bytes.view_bits_mut::<Msb0>()[256 - path.0.len()..].copy_from_bitslice(&path.0);
+                // SAFETY: byte array is 32 bytes long
                 let path_hash = Felt252Wrapper::try_from(&bytes).unwrap();
-                let mut length = [0; 32];
-                // Safe as len() is guaranteed to be <= 251
-                length[31] = path.0.len() as u8;
 
-                let length = Felt252Wrapper::try_from(&length).unwrap();
+                let length = Felt252Wrapper::from(path.0.len() as u8);
                 Felt252Wrapper(H::hash_elements(child.0, path_hash.0) + length.0)
             }
         }
@@ -1114,7 +1112,7 @@ impl<H: HasherT, DB: BonsaiDatabase, ID: Id> MerkleTree<H, DB, ID> {
 
         for proof_node in proofs.iter() {
             // Hash mismatch? Return None.
-            if proof_node.hash::<PedersenHasher>() != expected_hash {
+            if proof_node.hash::<H>() != expected_hash {
                 return None;
             }
             match proof_node {