Deny diagnostic lints in rustc_interface

compiler/rustc_interface/src/lib.rs

@@ -5,6 +5,8 @@
 #![feature(once_cell)]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 mod callbacks;
 mod errors;