Typescript compile-time codgen reflection validator

codegenValidator.ts

import * as moment from 'moment';

type ArrayLike = any[] & { length: number }; // { length?: number } extends any[] == true

type IsNullable<T>    = null extends T        ? true : false;
type IsUndefinable<T> = undefined extends T   ? true : false;
type Unwrap<T>        = T extends (infer U)[] ? U    : never;
type IsArray<T>       = T extends ArrayLike   ? true : false;

type EnumLike<T> =
	  IsNullable<T> extends true    ? never
	: IsUndefinable<T> extends true ? never
	: { [F in keyof T]: number; }
;

type DefaultMap = 'ignore';

type TypeValue<T, TNullable extends boolean, TUndefinable extends boolean> =
	T extends DefaultMap
	? TNullable extends true
		? TUndefinable extends true
			? 'null | undefined'
			: 'null'
		: TUndefinable extends true
			? 'undefined'
			: DefaultMap
	: T extends boolean         ? 'boolean'
	: T extends string          ? 'string'
	: T extends number          ? 'number'
	: T extends Date            ? 'date'
	: T extends moment.Moment   ? 'moment'
	: T extends moment.Duration ? 'moment-duration'
	: T extends {}              ? TypeInfo<T>
	: T extends any[]           ? ArrayFieldInfo<T, TNullable, TUndefinable>
	: T extends EnumLike<T>     ? 'number'
	: DefaultMap
;

type AboutField<TNullable extends boolean, TUndefinable extends boolean, TArray extends boolean> = {
	readonly isNullable: TNullable;
	readonly isUndefinable: TUndefinable;
	readonly isArray: TArray;
}

type Undefault<T> = T extends null | undefined ? DefaultMap : T;

type SimpleFieldInfo<T, TNullable extends boolean, TUndefinable extends boolean> =
	AboutField<TNullable, TUndefinable, false>
	& {
		readonly type: TypeValue<T, TNullable, TUndefinable>;
	}
;

type ArrayFieldInfo<T, TNullable extends boolean, TUndefinable extends boolean> =
	AboutField<TNullable, TUndefinable, true>
	& {
		item: RawField<Unwrap<T>>
	}
;

type FieldInfo<T, TNullable extends boolean, TUndefinable extends boolean> =
	true extends IsArray<T>
	? ArrayFieldInfo<T, TNullable, TUndefinable>
	: SimpleFieldInfo<T, TNullable, TUndefinable>
;

type RawField<T> = FieldInfo<Undefault<T>, IsNullable<T>, IsUndefinable<T>>; 

export type TypeInfo<T extends {}> = {
	readonly [F in keyof T]: RawField<T[F]>
} 

Жесть ты решил упороться =)