Fix unused attributes on macro_rules.

src/test/ui/unused/unused-attr-macro-rules.rs

@@ -0,0 +1,34 @@
+#![deny(unused_attributes)]
+// Unused attributes on macro_rules requires special handling since the
+// macro_rules definition does not survive towards HIR.
+
+// A sample of various built-in attributes.
+#[macro_export]
+#[macro_use] //~ ERROR unused attribute
+#[path="foo"] //~ ERROR unused attribute
+#[recursion_limit="1"] //~ ERROR unused attribute
+                       //~| ERROR crate-level attribute should be an inner attribute
+macro_rules! foo {
+    () => {};
+}
+
+// The following should not warn about unused attributes.
+#[allow(unused)]
+macro_rules! foo2 {
+    () => {};
+}
+
+#[cfg(FALSE)]
+macro_rules! foo {
+    () => {};
+}
+
+/// Some docs
+#[deprecated]
+#[doc = "more docs"]
+#[macro_export]
+macro_rules! bar {
+    () => {};
+}
+
+fn main() {}

src/test/ui/unused/unused-attr-macro-rules.stderr

@@ -0,0 +1,32 @@
+error: unused attribute
+  --> $DIR/unused-attr-macro-rules.rs:7:1
+   |
+LL | #[macro_use]
+   | ^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unused-attr-macro-rules.rs:1:9
+   |
+LL | #![deny(unused_attributes)]
+   |         ^^^^^^^^^^^^^^^^^
+
+error: unused attribute
+  --> $DIR/unused-attr-macro-rules.rs:8:1
+   |
+LL | #[path="foo"]
+   | ^^^^^^^^^^^^^
+
+error: unused attribute
+  --> $DIR/unused-attr-macro-rules.rs:9:1
+   |
+LL | #[recursion_limit="1"]
+   | ^^^^^^^^^^^^^^^^^^^^^^
+
+error: crate-level attribute should be an inner attribute: add an exclamation mark: `#![foo]`
+  --> $DIR/unused-attr-macro-rules.rs:9:1
+   |
+LL | #[recursion_limit="1"]
+   | ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
+