From 0369995364c04f9476dbedd55d50caf915017ea7 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Wed, 22 Jun 2022 15:11:18 -0400
Subject: [PATCH] tor-cell: convert BytesErr to a struct variant

---
 crates/tor-cell/semver.md             |  1 +
 crates/tor-cell/src/chancell/codec.rs |  5 ++++-
 crates/tor-cell/src/chancell/msg.rs   |  6 ++++--
 crates/tor-cell/src/err.rs            | 17 +++++++++++++----
 4 files changed, 22 insertions(+), 7 deletions(-)
 create mode 100644 crates/tor-cell/semver.md

diff --git a/crates/tor-cell/semver.md b/crates/tor-cell/semver.md
new file mode 100644
index 000000000..975fe642a
--- /dev/null
+++ b/crates/tor-cell/semver.md
@@ -0,0 +1 @@
+BREAKING: incompatible change to error variant
diff --git a/crates/tor-cell/src/chancell/codec.rs b/crates/tor-cell/src/chancell/codec.rs
index 862cb6827..fda5d1061 100644
--- a/crates/tor-cell/src/chancell/codec.rs
+++ b/crates/tor-cell/src/chancell/codec.rs
@@ -83,7 +83,10 @@ impl ChannelCodec {
     pub fn decode_cell(&mut self, src: &mut BytesMut) -> crate::Result<Option<ChanCell>> {
         /// Wrap `be` as an appropriate type.
         fn wrap_err(be: tor_bytes::Error) -> crate::Error {
-            crate::Error::BytesErr(be, "channel cell")
+            crate::Error::BytesErr {
+                err: be,
+                parsed: "channel cell",
+            }
         }
 
         if src.len() < 7 {
diff --git a/crates/tor-cell/src/chancell/msg.rs b/crates/tor-cell/src/chancell/msg.rs
index b3e21e2c7..8d8c0a77d 100644
--- a/crates/tor-cell/src/chancell/msg.rs
+++ b/crates/tor-cell/src/chancell/msg.rs
@@ -919,8 +919,10 @@ impl Certs {
             .cert_body(tp)
             .ok_or_else(|| crate::Error::ChanProto(format!("Missing {} certificate", tp)))?;
 
-        let cert = tor_cert::Ed25519Cert::decode(body)
-            .map_err(|be| crate::Error::BytesErr(be, "ed25519 certificate"))?;
+        let cert = tor_cert::Ed25519Cert::decode(body).map_err(|be| crate::Error::BytesErr {
+            err: be,
+            parsed: "ed25519 certificate",
+        })?;
         if cert.peek_cert_type() != tp {
             return Err(crate::Error::ChanProto(format!(
                 "Found a {} certificate labeled as {}",
diff --git a/crates/tor-cell/src/err.rs b/crates/tor-cell/src/err.rs
index eaff4f7a8..8dab9db52 100644
--- a/crates/tor-cell/src/err.rs
+++ b/crates/tor-cell/src/err.rs
@@ -12,8 +12,14 @@ use tor_error::{ErrorKind, HasKind};
 pub enum Error {
     /// An error that occurred in the tor_bytes crate while decoding an
     /// object.
-    #[error("Error while parsing {1}")]
-    BytesErr(#[source] tor_bytes::Error, &'static str),
+    #[error("Error while parsing {parsed}")]
+    BytesErr {
+        /// The error that occurred.
+        #[source]
+        err: tor_bytes::Error,
+        /// The thing that was being parsed.
+        parsed: &'static str,
+    },
     /// There was a programming error somewhere in the code.
     #[error("Internal programming error")]
     Internal(tor_error::Bug),
@@ -34,8 +40,11 @@ impl HasKind for Error {
         use Error as E;
         use ErrorKind as EK;
         match self {
-            E::BytesErr(ByE::Truncated, _) => EK::Internal,
-            E::BytesErr(_, _) => EK::TorProtocolViolation,
+            E::BytesErr {
+                err: ByE::Truncated,
+                ..
+            } => EK::Internal,
+            E::BytesErr { .. } => EK::TorProtocolViolation,
             E::Internal(_) => EK::Internal,
             E::ChanProto(_) => EK::TorProtocolViolation,
             E::BadStreamAddress => EK::BadApiUsage,