export type Option<T> = T | null;
export type Maybe<T> = Option<T> | undefined | void;

export type Factory<T> = new (...args: unknown[]) => T;

export const HAS_NATIVE_SYMBOL = (function () {
  if (typeof Symbol !== 'function') {
    return false;
  }

  // eslint-disable-next-line symbol-description
  return typeof Symbol() === 'symbol';
})();

export function keys<T>(obj: T): Array<keyof T> {
  return Object.keys(obj) as Array<keyof T>;
}

export function unwrap<T>(val: Maybe<T>): T {
  if (val === null || val === undefined) throw new Error(`Expected value to be present`);
  return val as T;
}

export function expect<T>(val: Maybe<T>, message: string): T {
  if (val === null || val === undefined) throw new Error(message);
  return val as T;
}

export function unreachable(message = 'unreachable'): Error {
  return new Error(message);
}

export function exhausted(value: never): never {
  throw new Error(`Exhausted ${value}`);
}

export type Lit = string | number | boolean | undefined | null | void | {};

export const tuple = <T extends Lit[]>(...args: T) => args;

export const symbol = HAS_NATIVE_SYMBOL
  ? Symbol
  : (key: string) => `__${key}${Math.floor(Math.random() * Date.now())}__` as any;

export type Option<T> = T | null;
export type Maybe<T> = Option<T> | undefined | void;

export type Factory<T> = new (...args: unknown[]) => T;

export function keys<T>(obj: T): Array<keyof T> {
  return Object.keys(obj) as Array<keyof T>;
}

export function unwrap<T>(val: Maybe<T>): T {
  if (val === null || val === undefined) throw new Error(`Expected value to be present`);
  return val as T;
}

export function expect<T>(val: Maybe<T>, message: string): T {
  if (val === null || val === undefined) throw new Error(message);
  return val as T;
}

export function unreachable(message = 'unreachable'): Error {
  return new Error(message);
}

export function exhausted(value: never): never {
  throw new Error(`Exhausted ${value}`);
}

export type Lit = string | number | boolean | undefined | null | void | {};

export const tuple = <T extends Lit[]>(...args: T) => args;

export const symbol =
  typeof Symbol !== 'undefined'
    ? Symbol
    : (key: string) => `__${key}${Math.floor(Math.random() * Date.now())}__` as any;

--- 
+++ 
@@ -2,6 +2,15 @@
 export type Maybe<T> = Option<T> | undefined | void;
 
 export type Factory<T> = new (...args: unknown[]) => T;
+
+export const HAS_NATIVE_SYMBOL = (function () {
+  if (typeof Symbol !== 'function') {
+    return false;
+  }
+
+  // eslint-disable-next-line symbol-description
+  return typeof Symbol() === 'symbol';
+})();
 
 export function keys<T>(obj: T): Array<keyof T> {
   return Object.keys(obj) as Array<keyof T>;
@@ -29,7 +38,6 @@
 
 export const tuple = <T extends Lit[]>(...args: T) => args;
 
-export const symbol =
-  typeof Symbol !== 'undefined'
-    ? Symbol
-    : (key: string) => `__${key}${Math.floor(Math.random() * Date.now())}__` as any;
+export const symbol = HAS_NATIVE_SYMBOL
+  ? Symbol
+  : (key: string) => `__${key}${Math.floor(Math.random() * Date.now())}__` as any;
[BUGFIX] Use custom symbol whenever native is not present

Uses the custom symbol logic whenever native is not present, preventing us
from using polyfills. This ensures that our polyfilled symbols have the
same assignment semantics as native symbols, specifically Object.assign.
