[ES8] async arrow function IIFE fix

lib/output.js

@@ -1039,11 +1039,11 @@ function OutputStream(options) {
         var needs_parens = parent instanceof AST_Binary ||
             parent instanceof AST_Unary ||
             (parent instanceof AST_Call && self === parent.expression);
+        if (needs_parens) { output.print("(") }
         if (self.async) {
             output.print("async");
             output.space();
         }
-        if (needs_parens) { output.print("(") }
         if (self.argnames.length === 1 && self.argnames[0] instanceof AST_Symbol) {
             self.argnames[0].print(output);
         } else {

test/compress/async.js

@@ -252,3 +252,12 @@ async_arrow_wait: {
     }
     expect_exact: "var a=async(x,y)=>await x(y);"
 }
+
+async_arrow_iife: {
+    input: {
+        (async () => {
+            await fetch({});
+        })();
+    }
+    expect_exact: "(async()=>{await fetch({})})();"
+}