Ensure helpers that reference globals continue to reference the globals properly.

packages/babel-core/src/transformation/file/index.js

@@ -246,7 +246,13 @@ export default class File extends Store {
       name,
     ));
 
-    const { nodes } = getHelper(name, uid, ownBindingNames);
+    const { nodes, globals } = getHelper(name, uid, ownBindingNames);
+
+    globals.forEach(name => {
+      if (this.path.scope.hasBinding(name, true /* noGlobals */)) {
+        this.path.scope.rename(name);
+      }
+    });
 
     nodes.forEach(node => {
       node._compact = true;

packages/babel-helpers/src/index.js

@@ -18,6 +18,7 @@ function makePath(path) {
  * the helper is whatever context it is needed in.
  */
 function getHelperMetadata(file) {
+  const globals = new Set();
   const localBindingNames = new Set();
 
   let exportName;
@@ -65,6 +66,12 @@ function getHelperMetadata(file) {
         localBindingNames.add(name);
       });
     },
+    ReferencedIdentifier(child) {
+      const name = child.node.name;
+      const binding = child.scope.getBinding(name);
+
+      if (!binding) globals.add(name);
+    },
     AssignmentExpression(child) {
       const left = child.get("left");
 
@@ -91,6 +98,7 @@ function getHelperMetadata(file) {
   exportBindingAssignments.reverse();
 
   return {
+    globals: Array.from(globals),
     localBindingNames: Array.from(localBindingNames),
     exportBindingAssignments,
     exportPath,
@@ -187,6 +195,7 @@ function loadHelper(name) {
 
       return {
         nodes: file.program.body,
+        globals: metadata.globals,
       };
     };
   }

packages/babel-plugin-transform-async-to-generator/src/index.js

@@ -9,13 +9,6 @@ export default function() {
       Function(path, state) {
         if (!path.node.async || path.node.generator) return;
 
-        // Ensure any Promise bindings at the Program level are renamed
-        // so the asyncToGenerator helper only sees the native Promise
-        const programScope = path.scope.getProgramParent();
-        if (programScope.hasBinding("Promise", true)) {
-          programScope.rename("Promise");
-        }
-
         remapAsyncToGenerator(path, state.file, {
           wrapAsync: state.addHelper("asyncToGenerator"),
         });