/**
 * A structure which can hold any value type, even undefined,
 * and can itself be const, while still allowing the value to
 * be added later.
 */
export interface Holder<T> {
    isPresent(): this is ValuedHolder<T>;
    setValue(value: T): unknown;
    readonly value: T | undefined;
}
/**
 * A {@link Holder} without a value, yet.
 */
export interface EmptyHolder<T> extends Holder<T> {
    setValue(value: T): asserts this is ValuedHolder<T>;
    readonly value: undefined;
}
/**
 * A {@link Holder} whose value has been set.
 */
export interface ValuedHolder<T> extends Holder<T> {
    setValue(value: T): never;
    readonly value: T;
}
export declare function holder<T>(value: T): ValuedHolder<T>;
export declare function holder<T>(): EmptyHolder<T>;
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