Add test file that creates a compiler error when hygiene is violated/stuff is used from outer scope

tarpc/tests/proc_macro_hygene.rs

@@ -0,0 +1,14 @@
+#![no_implicit_prelude]
+extern crate tarpc as some_random_other_name;
+
+#[::tarpc::derive_serde]
+#[derive(Debug, PartialEq, Eq)]
+pub enum TestData {
+    Black,
+    White,
+}
+
+#[::tarpc::service]
+pub trait ColorProtocol {
+    async fn get_opposite_color(color: u8) -> u8;
+}