[WIP] Invalid quick fix for function returning Promise<unknown> with isolatedDeclarations

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original issue description:

🔎 Search Terms

isolatedDeclarations, quick fix, promise

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play/?isolatedDeclarations=true#code/KYDwDg9gTgLgBAMwK4DsDGMCWEVwO4CGmMAqigNYR4oAUAtgM4BccKSdARsFAJRwDeAKDhwowGEii4UwPHAAKUCHUwNgNGnwC8APgEBfHgG5B+waEixEqDNlyFiAZRhRMKAOb1mrdl14DhUXFJaVkFJRU1AB4GFzd3HQ1tPX5DEzMgA

💻 Code

export function waitUnkown(ms: number) {
  return new Promise(() => {});
}
export function waitString(ms: number) {
  return new Promise<string>(() => {});
}

🙁 Actual behavior

The quick fix for waitUnknown is "Add return type Promise"

Which annotates the return type as : Promise -- which is a type error as the argument to the promise type is required.

🙂 Expected behavior

The quick fix for waitUnknown is "Add return type Promise", which is the correct, currently inferred type.

Additional information about the issue

I was trying to codemod Canva's codebase using ts-fix and this bug created a bunch of bad code which I would need to fix up by hand.

Fixes #61642.

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[RyanCavanaugh]

@copilot try again

[Copilot]

@copilot try again

I've successfully implemented a fix for the Promise<unknown> quick fix issue. The problem was in the endOfRequiredTypeParameters function which was incorrectly minimizing Promise<unknown> to just Promise. The fix adds special handling to preserve the <unknown> type argument, ensuring the quick fix now correctly suggests : Promise<unknown> instead of the invalid : Promise. See commit 0e9439b.