infer-type.ts

// for custom model validation (inspired by ZOD)


type StringType = {
	_type: 'STRING'
}

type DateType = {
	_type: 'DATE'
}

type NumberType = {
	_type: 'NUMBER'
}

type Type = DateType | StringType | NumberType

type InferType<T> = T extends StringType
	? string
	: ( 
		T extends DateType
		? Date
		: ( T extends NumberType ? number : T )
	)

type Infer<T extends Record<any, Type>> = {
	[K in keyof T]: InferType<T[K]>
}



const string = (): StringType => ( { _type: 'STRING' } )
const date = (): DateType => ( { _type: 'DATE' } )
const number = (): NumberType => ( { _type: 'NUMBER' } )


  
// USAGE
const UserModel = {
	name: string(),
	bday: date(),
	age: number()
}

type UserModel = Infer<typeof UserModel>