Warn when stores are used without $ prefix.

[TheCymaera]

Describe the problem

Occasionally, I forget to prefix stores with the $ symbol and don't find out until runtime.

Describe the proposed solution

Svelte should emit a warning when stores are used as values.

Alternatives considered

None.

Importance

nice to have

[brunnerh]

The problem is that there various intended uses without $, especially for custom stores that may have additional methods or properties.

[TheCymaera]

The problem is that there various intended uses without $, especially for custom stores that may have additional methods or properties.

I think the error should only apply to stores that are used as the final value in the HTML.

For other uses, regular type-checking should work fine.

[baseballyama]

I think this is not Svelte compiler's task.
I created new rule proposal at ESLint plugin.

sveltejs/eslint-plugin-svelte#282

[baseballyama]

This rule is implemented at v2.12.0 of eslint-plugin-svelte!

https://ota-meshi.github.io/eslint-plugin-svelte/rules/require-store-reactive-access/