Conditional type expression are indeed very powerful and, little known fact, can be used to generate types recursively. Here's a type signature from hell with

Conditional type expression are indeed very powerful and, little known fact, can be used to generate types recursively. Here's a type signature from hell with its usage: type Component = { type: 'a' } | { type: 'b' }; type FoundComponents<T extends any[]> = T extends [a: infer A] ? [Extract<Component, {type: A}>] : T extends [a: infer A, ...b: infer B ] ? [Extract<Component, {type: A}>, ...FoundComponents<B>] : never; export function findComponentSets<T extends Component['type'][]>(components: Component[], ...componentTypes: T ): FoundComponents<T>[]; export function findComponentSets(components: Component[], ...componentTypes: Component['type'][] ): Component[][] { return [] } It recursively picks outputs types based on the input parameters, so if you call e.g. findComponentSets([], 'a', 'b') the output type will be [{type: 'a'}, {type: 'b'}][]. I'm using it in an Entity Component System based game I'm writing to type check the function which receives a flat list of Components and type selectors and outputs a list of tuples with the selected Component types. findComponentSets(components, 'position', 'hit-box') .forEach(([position, hitBox]) => system.process(position, hitBox));