THRIFT-5360 Remove deprecated Error::description() methods (#2342)

Client: rs
diff --git a/lib/rs/src/errors.rs b/lib/rs/src/errors.rs
index 03d98cf..fc26330 100644
--- a/lib/rs/src/errors.rs
+++ b/lib/rs/src/errors.rs
@@ -17,7 +17,6 @@
 
 use std::convert::TryFrom;
 use std::convert::{From, Into};
-use std::error::Error as StdError;
 use std::fmt::{Debug, Display, Formatter};
 use std::{error, fmt, io, string};
 
@@ -146,11 +145,7 @@
 /// }
 ///
 /// // auto-generated by the Thrift compiler
-/// impl Error for Xception {
-///   fn description(&self) -> &str {
-///     "remote service threw Xception"
-///   }
-/// }
+/// impl Error for Xception { }
 ///
 /// // auto-generated by the Thrift compiler
 /// impl From<Xception> for thrift::Error {
@@ -162,7 +157,7 @@
 /// // auto-generated by the Thrift compiler
 /// impl Display for Xception {
 ///   fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-///     self.description().fmt(f)
+///     write!(f, "remote service threw Xception")
 ///   }
 /// }
 ///
@@ -270,16 +265,7 @@
     }
 }
 
-impl error::Error for Error {
-    fn description(&self) -> &str {
-        match *self {
-            Error::Transport(ref e) => TransportError::description(e),
-            Error::Protocol(ref e) => ProtocolError::description(e),
-            Error::Application(ref e) => ApplicationError::description(e),
-            Error::User(ref e) => e.description(),
-        }
-    }
-}
+impl error::Error for Error {}
 
 impl Debug for Error {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
@@ -370,6 +356,7 @@
 /// I/O error categories.
 ///
 /// This list may grow, and it is not recommended to match against it.
+#[non_exhaustive]
 #[derive(Clone, Copy, Eq, Debug, PartialEq)]
 pub enum TransportErrorKind {
     /// Catch-all I/O error.
@@ -388,9 +375,9 @@
     SizeLimit = 6,
 }
 
-impl TransportError {
-    fn description(&self) -> &str {
-        match self.kind {
+impl Display for TransportError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let error_text = match self.kind {
             TransportErrorKind::Unknown => "transport error",
             TransportErrorKind::NotOpen => "not open",
             TransportErrorKind::AlreadyOpen => "already open",
@@ -398,13 +385,9 @@
             TransportErrorKind::EndOfFile => "end of file",
             TransportErrorKind::NegativeSize => "negative size message",
             TransportErrorKind::SizeLimit => "message too long",
-        }
-    }
-}
+        };
 
-impl Display for TransportError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.description())
+        write!(f, "{}", error_text)
     }
 }
 
@@ -434,24 +417,24 @@
             | io::ErrorKind::ConnectionRefused
             | io::ErrorKind::NotConnected => Error::Transport(TransportError {
                 kind: TransportErrorKind::NotOpen,
-                message: err.description().to_owned(),
+                message: err.to_string(),
             }),
             io::ErrorKind::AlreadyExists => Error::Transport(TransportError {
                 kind: TransportErrorKind::AlreadyOpen,
-                message: err.description().to_owned(),
+                message: err.to_string(),
             }),
             io::ErrorKind::TimedOut => Error::Transport(TransportError {
                 kind: TransportErrorKind::TimedOut,
-                message: err.description().to_owned(),
+                message: err.to_string(),
             }),
             io::ErrorKind::UnexpectedEof => Error::Transport(TransportError {
                 kind: TransportErrorKind::EndOfFile,
-                message: err.description().to_owned(),
+                message: err.to_string(),
             }),
             _ => {
                 Error::Transport(TransportError {
                     kind: TransportErrorKind::Unknown,
-                    message: err.description().to_owned(), // FIXME: use io error's debug string
+                    message: err.to_string(), // FIXME: use io error's debug string
                 })
             }
         }
@@ -462,7 +445,7 @@
     fn from(err: string::FromUtf8Error) -> Self {
         Error::Protocol(ProtocolError {
             kind: ProtocolErrorKind::InvalidData,
-            message: err.description().to_owned(), // FIXME: use fmt::Error's debug string
+            message: err.to_string(), // FIXME: use fmt::Error's debug string
         })
     }
 }
@@ -498,6 +481,7 @@
 /// Runtime library error categories.
 ///
 /// This list may grow, and it is not recommended to match against it.
+#[non_exhaustive]
 #[derive(Clone, Copy, Eq, Debug, PartialEq)]
 pub enum ProtocolErrorKind {
     /// Catch-all runtime-library error.
@@ -518,9 +502,9 @@
     DepthLimit = 6,
 }
 
-impl ProtocolError {
-    fn description(&self) -> &str {
-        match self.kind {
+impl Display for ProtocolError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let error_text = match self.kind {
             ProtocolErrorKind::Unknown => "protocol error",
             ProtocolErrorKind::InvalidData => "bad data",
             ProtocolErrorKind::NegativeSize => "negative message size",
@@ -528,13 +512,9 @@
             ProtocolErrorKind::BadVersion => "invalid thrift version",
             ProtocolErrorKind::NotImplemented => "not implemented",
             ProtocolErrorKind::DepthLimit => "maximum skip depth reached",
-        }
-    }
-}
+        };
 
-impl Display for ProtocolError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.description())
+        write!(f, "{}", error_text)
     }
 }
 
@@ -589,6 +569,7 @@
 /// Auto-generated or user-implemented code error categories.
 ///
 /// This list may grow, and it is not recommended to match against it.
+#[non_exhaustive]
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum ApplicationErrorKind {
     /// Catch-all application error.
@@ -618,9 +599,9 @@
     UnsupportedClientType = 10, // ??
 }
 
-impl ApplicationError {
-    fn description(&self) -> &str {
-        match self.kind {
+impl Display for ApplicationError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let error_text = match self.kind {
             ApplicationErrorKind::Unknown => "service error",
             ApplicationErrorKind::UnknownMethod => "unknown service method",
             ApplicationErrorKind::InvalidMessageType => "wrong message type received",
@@ -632,13 +613,9 @@
             ApplicationErrorKind::InvalidTransform => "invalid transform",
             ApplicationErrorKind::InvalidProtocol => "invalid protocol requested",
             ApplicationErrorKind::UnsupportedClientType => "unsupported protocol client",
-        }
-    }
-}
+        };
 
-impl Display for ApplicationError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.description())
+        write!(f, "{}", error_text)
     }
 }