Represent helpers as simple modules.

packages/babel-core/src/tools/build-external-helpers.js

@@ -29,7 +29,18 @@ function buildGlobal(namespace, builder) {
   );
   const tree = t.program([
     t.expressionStatement(
-      t.callExpression(container, [helpers.get("selfGlobal")]),
+      t.callExpression(container, [
+        // typeof global === "undefined" ? self : global
+        t.conditionalExpression(
+          t.binaryExpression(
+            "===",
+            t.unaryExpression("typeof", t.identifier("global")),
+            t.stringLiteral("undefined"),
+          ),
+          t.identifier("self"),
+          t.identifier("global"),
+        ),
+      ]),
     ),
   ]);
 
@@ -131,16 +142,12 @@ function buildHelpers(body, namespace, whitelist) {
   helpers.list.forEach(function(name) {
     if (whitelist && whitelist.indexOf(name) < 0) return;
 
-    const key = t.identifier(name);
-    body.push(
-      t.expressionStatement(
-        t.assignmentExpression(
-          "=",
-          t.memberExpression(namespace, key),
-          helpers.get(name),
-        ),
-      ),
+    const { nodes } = helpers.get(
+      name,
+      t.memberExpression(namespace, t.identifier(name)),
     );
+
+    body.push(...nodes);
   });
 }
 export default function(

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

@@ -241,24 +241,18 @@ export default class File extends Store {
       return t.memberExpression(runtime, t.identifier(name));
     }
 
-    const ref = getHelper(name);
+    const ownBindingNames = Object.keys(this.scope.getAllBindings());
     const uid = (this.declarations[name] = this.scope.generateUidIdentifier(
       name,
     ));
 
-    if (t.isFunctionExpression(ref) && !ref.id) {
-      ref.body._compact = true;
-      ref.id = uid;
-      ref.type = "FunctionDeclaration";
-      this.path.unshiftContainer("body", ref);
-    } else {
-      ref._compact = true;
-      this.scope.push({
-        id: uid,
-        init: ref,
-        unique: true,
-      });
-    }
+    const { nodes } = getHelper(name, uid, ownBindingNames);
+
+    nodes.forEach(node => {
+      node._compact = true;
+    });
+
+    this.path.unshiftContainer("body", nodes);
 
     return uid;
   }