Add a test for rustc_deprecated

Author: varkor

src/test/ui/deprecation/rustc_deprecation-in-future.rs

@@ -0,0 +1,15 @@
+// ignore-tidy-linelength
+
+#![deny(deprecated_in_future)]
+
+#![feature(staged_api)]
+
+#![stable(feature = "rustc_deprecation-in-future-test", since = "1.0.0")]
+
+#[rustc_deprecated(since = "99.99.99", reason = "effectively never")]
+#[stable(feature = "rustc_deprecation-in-future-test", since = "1.0.0")]
+pub struct S;
+
+fn main() {
+    let _ = S; //~ ERROR use of item 'S' that will be deprecated in future version 99.99.99: effectively never
+}

src/test/ui/deprecation/rustc_deprecation-in-future.stderr

@@ -0,0 +1,14 @@
+error: use of item 'S' that will be deprecated in future version 99.99.99: effectively never
+  --> $DIR/rustc_deprecation-in-future.rs:14:13
+   |
+LL |     let _ = S; //~ ERROR use of item 'S' that will be deprecated in future version 99.99.99: effectively never
+   |             ^
+   |
+note: lint level defined here
+  --> $DIR/rustc_deprecation-in-future.rs:3:9
+   |
+LL | #![deny(deprecated_in_future)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+