refactor!: Refactor WireMsg::read_from_stream to avoid logic error

Previously we used `TryFrom` which we know will succeed thanks to our
assertions, however we don't want to allow for the possibility of
unexpected panics by using `unwrap` here.

Since we have asserted the pointer size though, we can reasonably
perform a lossy conversion with `as`, knowing that in fact nothing will
be lost.

BREAKING CHANGE: The `Error::UnexpectedError` variant has been removed.

src/error.rs

@@ -97,9 +97,6 @@ pub enum Error {
     /// Missing connection
     #[error("No connection to the dest peer")]
     MissingConnection,
-    /// A supposedly impossible internal error occurred
-    #[error("Unexpected internal error: {0}")]
-    UnexpectedError(String),
     /// Couldn't resolve Public IP address
     #[error("Unresolved Public IP address")]
     UnresolvedPublicIp,

src/wire_msg.rs

@@ -44,16 +44,9 @@ impl WireMsg {
         {
             compile_error!("You need an architecture capable of addressing 32-bit pointers");
         }
-        let data_length = match usize::try_from(msg_header.data_len()) {
-            Ok(s) => s,
-            Err(_) => {
-                return Err(Error::UnexpectedError(format!(
-                    // this should never happen due to preceding compilation error
-                    "unable to convert u32 '{}' to usize",
-                    msg_header.data_len()
-                )));
-            }
-        };
+        // we know we can convert without loss thanks to our assertions above
+        let data_length = msg_header.data_len() as usize;
+
         let mut data: Vec<u8> = vec![0; data_length];
         let msg_flag = msg_header.usr_msg_flag();