# Parser.OptionalOf

Binds a Parser for optional evaluation.

## Signatures

```ts
interface OptionalOf extends TypeFunction {
    readonly return: InputOf<this> extends infer P extends Any ? Optional<P> : never;
}
```

## Why

Higher-order grammar can reuse the no-consumption absent branch.

## Ownership and lifetime

TypeScript instantiates `OptionalOf` while parsing a string-literal input; partial results and unconsumed text exist only in the resulting type.

## Property: return

Computes this type lambda's parse result for its current input.

## Property: return: Why

The local type-function protocol evaluates each parser combinator through this member without a parallel runtime object.

## Property: return: Ownership and lifetime

TypeScript evaluates `OptionalOf.return` when the surrounding parser is applied; the associated result is erased and retains no input at runtime.