Latter type parameters are not suggested in constraints of the preceding ones

[Andarist]

🔎 Search Terms

type parameters constraints completions

🕗 Version & Regression Information

• This changed in Don't include completions for current and later parameters #52690

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.4.0-dev.20231120#code/GYVwdgxgLglg9mABFApgZygHgGIwE4aIoAeqYAJmogMoD0AVPbQDQ0oQLkB8AFAIYAuRLgJRWAIyHV2nAJSIA3gF8AUCqA

💻 Code

function test<First extends S/**/, Second>(a: First, b: Second) {}

🙁 Actual behavior

Second is not suggested at this marker

🙂 Expected behavior

I'd expect Second to be suggested since depending on the latter type parameters is valid (even if weird at times).

Additional information about the issue

This change was called out in comments of the PR that introduced this (initially it focused only on expression-space parameters) but I wonder if this is something that could be revisited. cc @zardoy

[zardoy]

I didn't remember the exact motivation for filtering them out, probably I just found these completions annoying myself as I couldn't imagine a case where you would write First extends Second, Second instead of First, Second extends First, though there are pretty complex function signatures that still do this (just Vue.extend for example). Since these completions don't cause any type-errors, I think it would be more correct to revert the change for type parameters as you suggest.

Ideally checker and completion modules should use more methods in common so it's easier to filter out completions that can cause type errors to avoid such misalignments as this one.