add another export default anonymous async function test

test/compress/export.js

@@ -425,5 +425,22 @@ export_default_anonymous_generator_not_call: {
     input: {
         export default function*(){}(foo);
     }
+    // agrees with `acorn` and `babylon 7`
     expect_exact: "export default function*(){};foo;"
 }
+
+export_default_anonymous_async_function_not_call: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default async function(){}(foo);
+    }
+    // agrees with `acorn` and `babylon 7`
+    expect_exact: "export default async function(){};foo;"
+}