/** Throw an error. */
export default function fatalError(msg: string): never {
  throw new Error(msg)
}

/**
 * Utility function used to achieve exhaustive type checks at compile time.
 *
 * If the type system is bypassed or this method will throw an exception
 * using the second parameter as the message.
 *
 * @param {x}       Placeholder parameter in order to leverage the type
 *                  system. Pass the variable which has been type narrowed
 *                  in an exhaustive check.
 *
 * @param {message} The message to be used in the runtime exception.
 *
 */
export function assertNever(x: never, message: string): never {
  throw new Error(message)
}

/** Throw an error. */
export default function fatalError(msg: string): never {
  throw new Error(msg)
}

--- 
+++ 
@@ -2,3 +2,20 @@
 export default function fatalError(msg: string): never {
   throw new Error(msg)
 }
+
+/**
+ * Utility function used to achieve exhaustive type checks at compile time.
+ *
+ * If the type system is bypassed or this method will throw an exception
+ * using the second parameter as the message.
+ *
+ * @param {x}       Placeholder parameter in order to leverage the type
+ *                  system. Pass the variable which has been type narrowed
+ *                  in an exhaustive check.
+ *
+ * @param {message} The message to be used in the runtime exception.
+ *
+ */
+export function assertNever(x: never, message: string): never {
+  throw new Error(message)
+}
Add type helper for exhaustive checks
