check attributes

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

.github/workflows/ci.yml

@@ -46,6 +46,12 @@ jobs:
         command:  check
         args: --no-default-features --features std
 
+    - name: check attributes
+      uses: actions-rs/cargo@v1
+      with:
+        command:  check
+        args: --features attributes
+
     - name: tests
       uses: actions-rs/cargo@v1
       with: