doc

web/packages/utils/ensure.ts

@@ -1,5 +1,10 @@
 /**
  * Throw an exception if the given value is `null` or `undefined`.
+ *
+ * This is different from TypeScript's built in null assertion operator `!` in
+ * that `ensure` involves a runtime check, and will throw if the given value is
+ * null-ish. On the other hand the TypeScript null assertion is only an
+ * indication to the type system and does not involve any runtime checks.
  */
 export const ensure = <T>(v: T | null | undefined): T => {
     if (v === null) throw new Error("Required value was null");