THRIFT-5158 Update Rust generator and Rust lib,test,tutorial to only support 2018 edition
Client: rs
Patch: Allen George

This closes #2078
diff --git a/lib/rs/src/server/mod.rs b/lib/rs/src/server/mod.rs
index f24c113..050feee 100644
--- a/lib/rs/src/server/mod.rs
+++ b/lib/rs/src/server/mod.rs
@@ -17,8 +17,8 @@
 
 //! Types used to implement a Thrift server.
 
-use protocol::{TInputProtocol, TMessageIdentifier, TMessageType, TOutputProtocol};
-use {ApplicationError, ApplicationErrorKind};
+use crate::protocol::{TInputProtocol, TMessageIdentifier, TMessageType, TOutputProtocol};
+use crate::{ApplicationError, ApplicationErrorKind};
 
 mod multiplexed;
 mod threaded;
@@ -91,19 +91,19 @@
     /// the response to `o`.
     ///
     /// Returns `()` if the handler was executed; `Err` otherwise.
-    fn process(&self, i: &mut dyn TInputProtocol, o: &mut dyn TOutputProtocol) -> ::Result<()>;
+    fn process(&self, i: &mut dyn TInputProtocol, o: &mut dyn TOutputProtocol) -> crate::Result<()>;
 }
 
 /// Convenience function used in generated `TProcessor` implementations to
 /// return an `ApplicationError` if thrift message processing failed.
 pub fn handle_process_result(
     msg_ident: &TMessageIdentifier,
-    res: ::Result<()>,
+    res: crate::Result<()>,
     o_prot: &mut dyn TOutputProtocol,
-) -> ::Result<()> {
+) -> crate::Result<()> {
     if let Err(e) = res {
         let e = match e {
-            ::Error::Application(a) => a,
+            crate::Error::Application(a) => a,
             _ => ApplicationError::new(ApplicationErrorKind::Unknown, format!("{:?}", e)),
         };
 
@@ -114,7 +114,7 @@
         );
 
         o_prot.write_message_begin(&ident)?;
-        ::Error::write_application_error_to_out_protocol(&e, o_prot)?;
+        crate::Error::write_application_error_to_out_protocol(&e, o_prot)?;
         o_prot.write_message_end()?;
         o_prot.flush()
     } else {