Apply suggestions from code review.

incrementalmerkletree/src/frontier.rs

@@ -203,8 +203,8 @@ impl<H, const DEPTH: u8> Frontier<H, DEPTH> {
 
     /// Constructs a new frontier from its constituent parts.
     ///
-    /// Returns `None` if the new frontier would exceed the maximum allowed depth or if the list of
-    /// ommers provided is not consistent with the position of the leaf.
+    /// Returns an error if the new frontier would exceed the maximum allowed depth or if the list
+    /// of ommers provided is not consistent with the position of the leaf.
     pub fn from_parts(position: Position, leaf: H, ommers: Vec<H>) -> Result<Self, FrontierError> {
         NonEmptyFrontier::from_parts(position, leaf, ommers).and_then(Self::try_from)
     }

incrementalmerkletree/src/lib.rs

@@ -425,7 +425,7 @@ impl Address {
         }
     }
 
-    /// Returns whether this address is the right-hand child of its parent
+    /// Returns whether this address is the left-hand child of its parent
     pub fn is_left_child(&self) -> bool {
         self.index & 0x1 == 0
     }

incrementalmerkletree/src/witness.rs

@@ -102,7 +102,7 @@ impl<H, const DEPTH: u8> IncrementalWitness<H, DEPTH> {
                 }
             })
             .take(self.filled.len())
-            .fold(0u64, |acc, addr| acc + 2u64.pow(addr.level().into()));
+            .fold(0u64, |acc, addr| acc + (1u64 << u8::from(addr.level())));
 
         self.witnessed_position()
             + leaves_to_cursor_start