Add test for useless_anonymous_reexport lint

Author: GuillaumeGomez

compiler/rustc_lint/messages.ftl

@@ -510,4 +510,4 @@ lint_opaque_hidden_inferred_bound = opaque type `{$ty}` does not satisfy its ass
 lint_opaque_hidden_inferred_bound_sugg = add this bound
 
 lint_useless_anonymous_reexport = useless anonymous re-export
-    .note = only anonymous re-exports of traits are useful, this is {$article} `${desc}`
+    .note = only anonymous re-exports of traits are useful, this is {$article} `{$desc}`

compiler/rustc_lint/src/lints.rs

@@ -1533,6 +1533,7 @@ pub struct UnusedAllocationMutDiag;
 
 #[derive(LintDiagnostic)]
 #[diag(lint_useless_anonymous_reexport)]
+#[note]
 pub struct UselessAnonymousReexportDiag {
     pub article: &'static str,
     pub desc: &'static str,

tests/ui/lint/anonymous-reexport.rs

@@ -0,0 +1,16 @@
+#![deny(useless_anonymous_reexport)]
+#![crate_type = "rlib"]
+
+mod my_mod {
+    pub trait Foo {}
+    pub type TyFoo = dyn Foo;
+    pub struct Bar;
+    pub type TyBar = Bar;
+}
+
+pub use self::my_mod::Foo as _;
+pub use self::my_mod::TyFoo as _;
+pub use self::my_mod::Bar as _; //~ ERROR
+pub use self::my_mod::TyBar as _; //~ ERROR
+#[allow(unused_imports)]
+use self::my_mod::TyBar as _;

tests/ui/lint/anonymous-reexport.stderr

@@ -0,0 +1,20 @@
+error: useless anonymous re-export
+  --> $DIR/anonymous-reexport.rs:13:1
+   |
+LL | pub use self::my_mod::Bar as _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/anonymous-reexport.rs:1:9
+   |
+LL | #![deny(useless_anonymous_reexport)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: useless anonymous re-export
+  --> $DIR/anonymous-reexport.rs:14:1
+   |
+LL | pub use self::my_mod::TyBar as _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+