@sinchsmb/ui-kit/src/utils/assertUnreachable.ts

UI kit for SinchSMB frontend

/* istanbul ignore file */

/**
 * A utility for checking that all values from enum have been processed into the switch case.
 *
 * For example you have enum:
 * ```
 * enum TestEnum {
 *   One,
 *   Two,
 *   Three
 * }
 * ```
 *
 * And want process all values from enum. You write something like this:
 * ```
 * const value: TestEnum = ...;
 *
 * switch (value) {
 *   case TestEnum.One: ...; break;
 *   case TestEnum.Two: ...; break;
 *   case TestEnum.Three: ...; break;
 * }
 * ```
 *
 * But you want protect this code from case when you add new value to enum and forgot process it in
 * switch-case. For this you can write:
 * ```
 * const value: TestEnum = ...;
 *
 * switch (value) {
 *   case TestEnum.One: ...; break;
 *   case TestEnum.Two: ...; break;
 *   case TestEnum.Three: ...; break;
 *   default: assertUnreachable(value);
 * }
 * ```
 *
 * And if you add `TestEnum.Four`, then you get TS error in `default`.
 *
 * @see https://stackoverflow.com/a/39419171/1778685
 */
export function assertUnreachable(value: never): never;
export function assertUnreachable<T>(value: T) {
  throw new Error(`Didn't expect: ${value}`);
}