Mapped Type + Recursive Type = Type instantiation is excessively deep and possibly infinite (2589)

[yoni-rapoport]

Bug Report

This is the simplest repro of an issue that prevents the use of recursive mapped types for any type that contain any properties (or properties of properties etc...) typed using a recursive type alias.

🔎 Search Terms

• Type Alias
• Mapped Types
• Recursive Types
• Type instantiation is excessively deep and possibly infinite

🕗 Version & Regression Information

Since 3.7

⏯ Playground Link

Playground Link

💻 Code

type RecursiveType = string | number | RecursiveType[];

type MappedType<T> = {
  [K in keyof T]: MappedType<T[K]>;
};

type MappedTypeOfRecursiveType = MappedType<RecursiveType>;

🙁 Actual behavior

Type instantiation is excessively deep and possibly infinite. (2589)

🙂 Expected behavior

Expected to compile successfully

[orouz]

somehow it works with a key remapping of K to K

Playground

also worth looking into #45025

[Gregoor]

I am running into this right now as well, and can confirm that it's still a problem with both v4 and v5.