export declare class InvalidPercentageError extends Error {
}
export declare class NullishError extends Error {
}
export declare const assertNonNullish: <T>(value: T, message?: string) => asserts value is NonNullable<T>;
export declare const asNonNullish: <T>(value: T, message?: string) => NonNullable<T>;
export declare const assertPercentageNumber: (percentage: number) => void;
/**
 * Utility to enforce exhaustiveness checks in TypeScript.
 *
 * This function should only be called in branches of a `switch` or conditional
 * that should be unreachable if the union type has been fully handled.
 *
 * By typing the parameter as `never`, the compiler will emit an error if
 * a new variant is added to the union but not covered in the logic.
 *
 * @param _ - A value that should be of type `never`. If this is not the case,
 *            the TypeScript compiler will flag a type error.
 * @param message - Optional custom error message to include in the thrown error.
 * @throws {Error} Always throws when invoked at runtime.
 *
 */
export declare const assertNever: (_: never, message?: string) => never;