Make client starts return an error

When returning, the Client would return an Ok(()). Instead, return an
error, since there is currently no reason the client would return under
"okay" circumstances.

src/client/error.rs

@@ -21,6 +21,9 @@ pub enum Error {
     /// When a shard has completely failed to reboot after resume and/or
     /// reconnect attempts.
     ShardBootFailure,
+    /// When all shards that the client is responsible for have shutdown with an
+    /// error.
+    Shutdown,
 }
 
 impl Display for Error {
@@ -34,6 +37,7 @@ impl StdError for Error {
         match *self {
             Error::InvalidToken => "The provided token was invalid",
             Error::ShardBootFailure => "Failed to (re-)boot a shard",
+            Error::Shutdown => "The clients shards shutdown",
         }
     }
 }

src/client/mod.rs

@@ -347,6 +347,12 @@ impl Client {
     /// # }
     /// ```
     ///
+    /// # Errors
+    ///
+    /// Returns a [`ClientError::Shutdown`] when all shards have shutdown due to
+    /// an error.
+    ///
+    /// [`ClientError::Shutdown`]: enum.ClientError.html#variant.Shutdown
     /// [gateway docs]: gateway/index.html#sharding
     pub fn start_autosharded(&mut self) -> Result<()> {
         let mut res = http::get_bot_gateway()?;
@@ -419,6 +425,12 @@ impl Client {
     /// # }
     /// ```
     ///
+    /// # Errors
+    ///
+    /// Returns a [`ClientError::Shutdown`] when all shards have shutdown due to
+    /// an error.
+    ///
+    /// [`ClientError::Shutdown`]: enum.ClientError.html#variant.Shutdown
     /// [`start`]: #method.start
     /// [`start_autosharded`]: #method.start_autosharded
     /// [gateway docs]: gateway/index.html#sharding
@@ -462,6 +474,12 @@ impl Client {
     /// # }
     /// ```
     ///
+    /// # Errors
+    ///
+    /// Returns a [`ClientError::Shutdown`] when all shards have shutdown due to
+    /// an error.
+    ///
+    /// [`ClientError::Shutdown`]: enum.ClientError.html#variant.Shutdown
     /// [`start_shard`]: #method.start_shard
     /// [`start_shard_range`]: #method.start_shard_range
     /// [Gateway docs]: gateway/index.html#sharding
@@ -516,6 +534,13 @@ impl Client {
     /// # }
     /// ```
     ///
+    /// # Errors
+    ///
+    /// Returns a [`ClientError::Shutdown`] when all shards have shutdown due to
+    /// an error.
+    ///
+    ///
+    /// [`ClientError::Shutdown`]: enum.ClientError.html#variant.Shutdown
     /// [`start_shard`]: #method.start_shard
     /// [`start_shards`]: #method.start_shards
     /// [Gateway docs]: gateway/index.html#sharding
@@ -919,7 +944,15 @@ impl Client {
     // 2: total number of shards the bot is sharding for
     //
     // Not all shards need to be initialized in this process.
-    fn start_connection(&mut self, shard_data: Option<[u64; 3]>, url: String) -> Result<()> {
+    //
+    // # Errors
+    //
+    // Returns a [`ClientError::Shutdown`] when all shards have shutdown due to
+    // an error.
+    //
+    // [`ClientError::Shutdown`]: enum.ClientError.html#variant.Shutdown
+    fn start_connection(&mut self, shard_data: Option<[u64; 3]>, url: String)
+        -> Result<()> {
         // Update the framework's current user if the feature is enabled.
         //
         // This also acts as a form of check to ensure the token is correct.
@@ -1012,7 +1045,7 @@ impl Client {
             let _ = thread.join();
         }
 
-        Ok(())
+        Err(Error::Client(ClientError::Shutdown))
     }
 }