[helpers ts conversion] temporal dead zone

packages/babel-helpers/src/helpers/tdz.js → packages/babel-helpers/src/helpers/tdz.ts

@@ -1,5 +1,5 @@
 /* @minVersion 7.5.5 */
 
-export default function _tdzError(name) {
+export default function _tdzError(name: string): never {
   throw new ReferenceError(name + " is not defined - temporal dead zone");
 }

packages/babel-helpers/src/helpers/temporalRef.ts

@@ -0,0 +1,8 @@
+/* @minVersion 7.0.0-beta.0 */
+
+import undef from "./temporalUndefined.ts";
+import err from "./tdz.ts";
+
+export default function _temporalRef<T>(val: T, name: string) {
+  return val === undef ? err(name) : val;
+}

packages/babel-helpers/src/helpers/temporalUndefined.js → packages/babel-helpers/src/helpers/temporalUndefined.ts

@@ -2,4 +2,4 @@
 
 // This function isn't mean to be called, but to be used as a reference.
 // We can't use a normal object because it isn't hoisted.
-export default function _temporalUndefined() {}
+export default function _temporalUndefined(): void {}