print deprecation message for -Car too

Author: klensy

compiler/rustc_session/src/options.rs

@@ -1553,7 +1553,8 @@ options! {
     // tidy-alphabetical-start
     #[rustc_lint_opt_deny_field_access("documented to do nothing")]
     ar: String = (String::new(), parse_string, [UNTRACKED],
-        "this option is deprecated and does nothing"),
+        "this option is deprecated and does nothing",
+        deprecated_do_nothing: true),
     #[rustc_lint_opt_deny_field_access("use `Session::code_model` instead of this field")]
     code_model: Option<CodeModel> = (None, parse_code_model, [TRACKED],
         "choose the code model to use (`rustc --print code-models` for details)"),

tests/ui/deprecation/deprecated_ar.rs

@@ -0,0 +1,4 @@
+//@ check-pass
+//@ compile-flags: -Car=foo
+
+fn main() {}

tests/ui/deprecation/deprecated_ar.stderr

@@ -0,0 +1,2 @@
+warning: `-C ar`: this option is deprecated and does nothing
+