Invert diagnostic lints.

That is, change `diagnostic_outside_of_impl` and
`untranslatable_diagnostic` from `allow` to `deny`, because more than
half of the compiler has be converted to use translated diagnostics.

This commit removes more `deny` attributes than it adds `allow`
attributes, which proves that this change is warranted.

clippy_config/src/lib.rs

@@ -4,7 +4,9 @@
 #![allow(
     clippy::must_use_candidate,
     clippy::missing_panics_doc,
-    rustc::untranslatable_diagnostic_trivial
+    rustc::diagnostic_outside_of_impl,
+    rustc::untranslatable_diagnostic,
+    rustc::untranslatable_diagnostic_trivial,
 )]
 
 extern crate rustc_ast;

clippy_lints/src/lib.rs

@@ -10,7 +10,12 @@
 #![feature(stmt_expr_attributes)]
 #![recursion_limit = "512"]
 #![cfg_attr(feature = "deny-warnings", deny(warnings))]
-#![allow(clippy::missing_docs_in_private_items, clippy::must_use_candidate)]
+#![allow(
+    clippy::missing_docs_in_private_items,
+    clippy::must_use_candidate,
+    rustc::diagnostic_outside_of_impl,
+    rustc::untranslatable_diagnostic,
+)]
 #![warn(trivial_casts, trivial_numeric_casts)]
 // warn on lints, that are included in `rust-lang/rust`s bootstrap
 #![warn(rust_2018_idioms, unused_lifetimes)]

clippy_utils/src/lib.rs

@@ -8,7 +8,13 @@
 #![feature(assert_matches)]
 #![recursion_limit = "512"]
 #![cfg_attr(feature = "deny-warnings", deny(warnings))]
-#![allow(clippy::missing_errors_doc, clippy::missing_panics_doc, clippy::must_use_candidate)]
+#![allow(
+    clippy::missing_errors_doc,
+    clippy::missing_panics_doc,
+    clippy::must_use_candidate,
+    rustc::diagnostic_outside_of_impl,
+    rustc::untranslatable_diagnostic,
+)]
 // warn on the same lints as `clippy_lints`
 #![warn(trivial_casts, trivial_numeric_casts)]
 // warn on lints, that are included in `rust-lang/rust`s bootstrap

src/driver.rs

@@ -1,3 +1,5 @@
+#![allow(rustc::diagnostic_outside_of_impl)]
+#![allow(rustc::untranslatable_diagnostic)]
 #![feature(rustc_private)]
 #![feature(let_chains)]
 #![feature(lazy_cell)]