Generic conditional type prematurely resolves to one of the branches instead of deferring

🔎 Search Terms

generic, conditional, premature / eager / defer, inline,

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about generic conditional types

⏯ Playground Link

Playground link

💻 Code

type IsNumber<T> = [T] extends [number] ? true : false
type IsFalse<T extends boolean> = false[] extends T[] ? true : false

type Direct = IsFalse<IsNumber<string>> extends true ? 0 : 1;
//   ^? type Direct = 0

type Shortcut<T> = IsFalse<IsNumber<T>> extends true ? 0 : 1;
type Indirect = Shortcut<string>;
//   ^? type Indirect = 1

🙁 Actual behavior

Direct and Indirect are different.

🙂 Expected behavior

Direct and Indirect should be the same because Direct is just an inlined version of Shortcut<string>.

Additional information about the issue

This feels like a similar issue to #39364, #30708, #30020 and maybe some others, but many of those have been resolved already and yet this one remains. Came from this Stack Overflow question.