Inference failure in <T>(f: (get: () => T) => T) => T

[devanshj]

🔎 Search Terms

Similar/duplicate of #49618, #47599 & #30134. Sorry couldn't come up with a better title.

🕗 Version & Regression Information

Tested with TypeScript 5.7.2

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/CYUwxgNghgTiAEYD2A7AzgF0XKGQC54AeAFQD4AKAM0IoHMQNaBKeAXjPhNY6585IAoQREbwMABnbYQuEBQr94AImXNBAeg3x4APQD8w0VgwBGaWBx4KAfXadV6rToNA

💻 Code

declare const create: <T>(f: (get: () => T) => T) => T

let t0 = create(() => "")
//  ^? string

let t1 = create(_ => "")
//  ^? unknown

🙁 Actual behavior

t1 is inferred as unknown

🙂 Expected behavior

t1 should be inferred as string

Additional information about the issue

This is a minimal reproduction of zustand's create...

import { create } from "zustand"

let t0 = create(() => "")
//  ^? UseBoundStore<StoreApi<string>>

let t1 = create(_ => "")
//  ^? UseBoundStore<StoreApi<unknown>>

I'm certain this is a duplicate of one of the above mentioned issue I just want to know it's duplicate of which issue exactly

[Andarist]

It looks to me like a duplicate of #49618 . There were also 2 other issues, similar to this one, reported recently: #60922 , #60544 . Despite those 2 mentioning NoInfer, the root cause of the issue is quite the same as here: resolving contextual parameter type that references a type parameter "fixes" its inference, it can't be changed afterward and the return type is not known at all before this point because it can only be computed after analyzing the function's body and that requires resolving the parameter's type