Add a test for duplicated attributes on use items

Author: topecongiro

tests/source/imports.rs

@@ -93,3 +93,7 @@ use a::{b::{c::{xxx, yyy, zzz}}};
 /// This line is not affected.
 // This line is deleted.
 use c;
+
+// #2670
+#[macro_use]
+use imports_with_attr;

tests/target/imports.rs

@@ -105,3 +105,7 @@ use a::b::c::{xxx, yyy, zzz};
 /// This line is not affected.
 // This line is deleted.
 use c;
+
+// #2670
+#[macro_use]
+use imports_with_attr;