# let

Adds a fixed property to every matched record output.

## Signatures

```ts
export { let_ as let };
```

```ts
declare const let_: {
    <K extends PropertyKey, B>(key: K, value: B): <G extends GuardInput<any, any, any, any>>(guard: G & RecordOutputConstraint<NoInfer<Guard.Output<G>>> & (K extends NoInfer<Guard.Output<G> extends infer O ? (O extends unknown ? keyof O : never) : never> ? never : unknown)) => Guard<Guard.Input<G>, Guard.Output<G> & {
        [k in K]: B;
    }, Guard.Error<G>, Guard.Services<G>>;
    <G extends GuardInput<any, any, any, any>, K extends PropertyKey, B>(guard: G & RecordOutputConstraint<NoInfer<Guard.Output<G>>>, key: Exclude<K, NoInfer<Guard.Output<G> extends infer O ? (O extends unknown ? keyof O : never) : never>>, value: B): Guard<Guard.Input<G>, Guard.Output<G> & {
        [k in K]: B;
    }, Guard.Error<G>, Guard.Services<G>>;
};
```

## Why

Record construction does not mutate the input and rejects existing enumerable keys; it returns an unfrozen plain object containing own enumerable string and symbol properties while dropping prototypes and non-enumerables.

## Ownership and lifetime

This pure combinator acquires no resources and creates a fresh plain object for every match.

## Examples

```ts
import { bindTo, let as letGuard, liftPredicate } from "@typed/guard"
const named = letGuard(bindTo(liftPredicate(Boolean), "value"), "kind", "input")
```