Use same error type for connect and connection

Author: Ulf Lilleengen

embedded-nal-async/src/stack/tcp.rs

@@ -175,10 +175,11 @@ impl<T: TcpClientStack> TcpClientStack for &mut T {
 /// this trait allows creating multiple connections using the same TCP/IP stack.
 pub trait TcpConnect {
 	/// Error type returned on connect failure.
-	type Error;
+	type Error: core::fmt::Debug;
 
 	/// Type holding state of a TCP connection.
-	type Connection<'m>: embedded_io::asynch::Read + embedded_io::asynch::Write
+	type Connection<'m>: embedded_io::asynch::Read<Error = Self::Error>
+		+ embedded_io::asynch::Write<Error = Self::Error>
 	where
 		Self: 'm;
 	/// Future returned by `connect` function.