Deprecated proc_macro doesn't trigger warning on build library

src/libsyntax_ext/proc_macro_harness.rs

@@ -416,6 +416,16 @@ fn mk_decls(
     ).map(|mut i| {
         let attr = cx.meta_word(span, sym::rustc_proc_macro_decls);
         i.attrs.push(cx.attribute(attr));
+
+        let deprecated_attr = attr::mk_nested_word_item(
+            Ident::new(sym::deprecated, span)
+        );
+        let allow_deprecated_attr = attr::mk_list_item(
+            Ident::new(sym::allow, span),
+            vec![deprecated_attr]
+        );
+        i.attrs.push(cx.attribute(allow_deprecated_attr));
+
         i
     });
 

src/test/ui/proc-macro/proc-macro-deprecated-attr.rs

@@ -0,0 +1,15 @@
+// build-pass
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::*;
+
+#[proc_macro]
+#[deprecated(since = "1.0.0", note = "test")]
+pub fn test_compile_without_warning_with_deprecated(_: TokenStream) -> TokenStream {
+    "
+    extern crate proc_macro;
+    fn foo() { }
+    ".parse().unwrap()
+}