feat: Restrict types for Spring and Tween

[webJose]

Closes Improve Spring data typing, or improving it so it doesn't bother about unsupported data types #14851

This PR introduces the MotionPrimitive and MotionRecord data types to accurately reflect what the algorithms of the Spring and Tween classes can handle.

The alternative would be to remove the throwing whenever an unsupported data type is found, but I suppose that is a breaking change and if that's the preferred route, then it would have to wait for Svelte v6. Therfore, this PR should greatly increase the accuracy of Intellisense when using Spring and Tween.

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.
• If this PR changes code within packages/svelte/src, add a changeset (npx changeset).

Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

⚠️ No Changeset found

Latest commit: f0a6b6d

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@14862

[webJose]

PR in draft mode. Kindly let me know if this is something the core team would like to pursue. If so, I'll follow any additional instructions I am given and take the PR out of draft mode. Thanks!

[Ocean-OS]

One thing to account for is that arrays containing numbers are supported, so perhaps MotionRecord could be changed to include arrays like so:

export type MotionRecord = {
	[x: string | number]: MotionPrimitive | MotionRecord | (MotionPrimitive | MotionRecord)[];
} | (MotionPrimitive | MotionRecord)[]

[webJose]

One thing to account for is that arrays containing numbers are supported, so perhaps MotionRecord could be changed to include arrays like so:

export type MotionRecord = {
	[x: string | number]: MotionPrimitive | MotionRecord | (MotionPrimitive | MotionRecord)[];
} | (MotionPrimitive | MotionRecord)[]

It's already accounted for. T extends from MotionRecord[string], which is MotionPrimitive, MotionRecord or arrays containing either of those. You can test this in the TS playground.

[webJose]

Maintainers, I remember Rich removed the throwing part when the type is not springable in the Spring class. I suppoose that this PR needs ammending to account for this (typing is no longer needed for Spring).

Do let me know if you want to proceed with this for Tween. I'll close it otherwise.