import { EastFunction, IfNullFunction, Variable } from '../functions';
import { EastTypeOf, NonNullable, Nullable, PrimitiveValue } from '../types';
/**
 * Return x1 of predicate is null, or x2 otherwise
 *
 * @param input the nullable {@link Expression} to test
 * @param out_null the return value if `input` is `null`
 * @param out_value a function of `value` to evaluate if `input` is not `null` (defaults to `value => value`)
 *
 * @category Expression
 *
 * @example
 * ```typescript
 *  // if name is null, replace with 'Unknown' string
 *  IfNull(
 *      name,
 *      Const('Unknown')
 *  )
 *  // if name is null, replace with 'UNKNOWN' string, otherwise make it uppercase
 *  IfNull(
 *      name,
 *      Const('UNKNOWN'),
 *      non_null_name => UpperCase(non_null_name)
 *  )
 * ```
 */
export declare function IfNull<T extends Nullable, N extends PrimitiveValue, V extends (x: Variable<NonNullable<T>>) => EastFunction>(input: EastFunction<T>, out_null: N, out_value: V & ((EastTypeOf<N> & ReturnType<V>["type"]) extends never ? never : unknown)): IfNullFunction<EastTypeOf<N>> & IfNullFunction<ReturnType<V>["type"]>;
export declare function IfNull<T extends Nullable, N extends EastFunction, V extends (x: Variable<NonNullable<T>>) => EastFunction>(input: EastFunction<T>, out_null: N, out_value: V & ((N["type"] & ReturnType<V>["type"]) extends never ? never : unknown)): IfNullFunction<N["type"]> & IfNullFunction<ReturnType<V>["type"]>;
export declare function IfNull<T extends Nullable, N extends PrimitiveValue>(input: EastFunction<T>, out_null: N & ((EastTypeOf<N> & T) extends never ? never : unknown)): IfNullFunction<EastTypeOf<N>> & IfNullFunction<NonNullable<T>>;
export declare function IfNull<T extends Nullable, N extends EastFunction>(input: EastFunction<T>, out_null: N & ((N["type"] & T) extends never ? never : unknown)): IfNullFunction<N["type"] & NonNullable<T>>;