/**
 *
 * To test if an object is void,
 * unlike undefined or null, testing o !== void
 * will not restrict the type.
 *
 * Example:
 *
 * declare o: { p: string; } | void;
 *
 * matchVoid(o)?null:o.p <== Type inference ok
 *
 * Match void
 * @param o type of o should be a union of type containing void
 * @returns true if o is void'ish ( null or undefined )
 */
export declare function matchVoid(o: any): o is void;