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Comment by hinkley | Hacker News Reader

Elixir and a few other languages have the pattern matching and type system that could pull that off but not a lot of languages do. Can you do that in typescript? I don’t see how.

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You can, using `function $<S>(sel: S | `${S}${ ' '|'#'|'.'|'[' }${string}`): HTMLElementMap[T];` or

    export type inferSelectorElementName<sel extends selector> =
    | string extends sel ? HTMLElement
      : sel extends `${infer A},${infer B}` ? inferSelectorElementName<A | B>
        : sel extends `${infer A}${'.' | '[' | '#'}${infer _}` ? inferSelectorElementName<A>
          : sel

    export type inferElementFromSelector<sel extends selector> =
    | string extends sel ? HTMLElement
      : inferSelectorElementName<sel> extends infer S ?
        S extends '' ? HTMLElement
          : S extends keyof HTMLElementTagNameMap ? HTMLElementTagNameMap[S]
            : never
        : never

TS types may go quite deep Check Arktype library [https://arktype.io/], it's type definitions are basically a Typescript written in JSON

    const user = type({
        name: "string",
        platform: "'android' | 'ios'",
        "version?": "number | string"
    })

TypeScript's type system is Turing complete, so you can not only do that, but also some insane stuff like:

- A SQL database implemented purely in TypeScript type system (https://github.com/codemix/ts-sql)

- Chess implemented entirely in TypeScript (and Rust) type systems (https://github.com/Dragon-Hatcher/type-system-chess)

- Lambda calculus in TypeScript type system (https://ayazhafiz.com/articles/21/typescript-type-system-lam...)

You definitely can do that in TypeScript. The kinds of things you can do with generic inference and string literals are crazy

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