core.assertnever | Medplum
assertNever() function
Checks that a value has type never. Useful for ensuring exhaustive matches.
Signature:
export declare function assertNever(value: never): never;
Parameters
| Parameter | Type | Description |
|---|---|---|
| value | never | The value that should never be present |
Returns:
never
Example
type MyUnion = 'a' | 'b' | 'c'
function f(arg: MyUnion) {
if (arg === 'a') { return 1; }
if (arg === 'b') { return 2; }
assertNever(arg); // Type error: 'c' is unhandled
}