turn inserted helper declarations into function declarations if possible

src/babel/generation/index.js

@@ -232,14 +232,14 @@ class CodeGenerator {
       this.map.mark(node, "end");
       if (opts.after) opts.after();
 
+      this.format.concise = oldConcise;
+
       newline(false);
 
       this.printTrailingComments(node, parent);
     } else {
       throw new ReferenceError(`unknown node of type ${JSON.stringify(node.type)} with constructor ${JSON.stringify(node && node.constructor.name)}`);
     }
-
-    this.format.concise = oldConcise;
   }
 
   printJoin(print, nodes, opts = {}) {

src/babel/transformation/file/index.js

@@ -370,13 +370,23 @@ export default class File {
     }
 
     var ref = util.template("helper-" + name);
-    ref._compact = true;
+
     var uid = this.declarations[name] = this.scope.generateUidIdentifier(name);
-    this.scope.push({
-      id: uid,
-      init: ref,
-      unique: true
-    });
+
+    if (t.isFunctionExpression(ref) && !ref.id) {
+      ref.body._compact = true;
+      ref._generated = 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
+      });
+    }
     return uid;
   }