fixup! Preserve and format type aliases in extern blocks

Author: ayazhafiz

rustfmt-core/rustfmt-lib/src/items.rs

@@ -1935,6 +1935,9 @@ pub(crate) fn rewrite_type_alias(
         let lhs = format!("{}=", prefix);
         rewrite_assign_rhs(context, lhs, &**ty, shape).map(|s| s + ";")
     } else {
+        if !generics.where_clause.predicates.is_empty() {
+            prefix.push_str(&indent.to_string_with_newline(context.config));
+        }
         Some(format!("{};", prefix))
     }
 }

rustfmt-core/rustfmt-lib/tests/target/issue-4159.rs

@@ -3,11 +3,13 @@ extern "C" {
 
     type A<'a>
     where
-        'a: 'static,;
+        'a: 'static,
+    ;
 
     type A<T: Ord>
     where
-        T: 'static,;
+        T: 'static,
+    ;
 
     type A = u8;