add in support for AwaitExpression "delegation"

lib/6to5/generation/generators/expressions.js

@@ -87,7 +87,11 @@ exports.CallExpression = function (node, print) {
 var buildYieldAwait = function (keyword) {
   return function (node, print) {
     this.push(keyword);
-    if (node.delegate) this.push("*");
+
+    if (node.delegate || node.all) {
+      this.push("*");
+    }
+
     if (node.argument) {
       this.space();
       print(node.argument);

lib/6to5/transformation/helpers/remap-async-to-generator.js

@@ -9,6 +9,12 @@ var visitor = {
 
     if (t.isAwaitExpression(node)) {
       node.type = "YieldExpression";
+
+      if (node.all) {
+        // await* foo; -> yield Promise.all(foo);
+        node.all = false;
+        node.argument = t.callExpression(t.memberExpression(t.identifier("Promise"), t.identifier("all")), [node.argument]);
+      }
     }
   }
 };