1 files changed, 56 insertions, 0 deletions
diff --git a/tests/ui/proc-macro/derive-helper-shadowing.rs b/tests/ui/proc-macro/derive-helper-shadowing.rs
new file mode 100644
index 000000000..80d982d25
--- /dev/null
+++ b/tests/ui/proc-macro/derive-helper-shadowing.rs
@@ -0,0 +1,56 @@
+// edition:2018
+// aux-build:test-macros.rs
+// aux-build:derive-helper-shadowing.rs
+
+#[macro_use]
+extern crate test_macros;
+#[macro_use]
+extern crate derive_helper_shadowing;
+
+use test_macros::empty_attr as empty_helper;
+
+macro_rules! gen_helper_use {
+    () => {
+        #[empty_helper] //~ ERROR cannot find attribute `empty_helper` in this scope
+        struct W;
+    }
+}
+
+#[empty_helper] //~ ERROR `empty_helper` is ambiguous
+                //~| WARN derive helper attribute is used before it is introduced
+                //~| WARN this was previously accepted
+#[derive(Empty)]
+struct S {
+    #[empty_helper] // OK, no ambiguity, derive helpers have highest priority
+    field: [u8; {
+        use empty_helper; //~ ERROR `empty_helper` is ambiguous
+
+        #[empty_helper] // OK, no ambiguity, derive helpers have highest priority
+        struct U;
+
+        mod inner {
+            // OK, no ambiguity, the non-helper attribute is not in scope here, only the helper.
+            #[empty_helper]
+            struct V;
+
+            gen_helper_use!();
+
+            #[derive(GenHelperUse)] //~ ERROR cannot find attribute `empty_helper` in this scope
+            struct Owo;
+
+            use empty_helper as renamed;
+            #[renamed] //~ ERROR cannot use a derive helper attribute through an import
+            struct Wow;
+        }
+
+        0
+    }]
+}
+
+// OK, no ambiguity, only the non-helper attribute is in scope.
+#[empty_helper]
+struct Z;
+
+fn main() {
+    let s = S { field: [] };
+}