Narrowing type not work in reactive statements

[yoyo930021]

Before You File a Bug Report Please Confirm You Have Done The Following...

• I'm using eslint-plugin-svelte. (*.svelte file linting does not work with the parser alone. You should also use eslint-plugin-svelte with it.)
• I'm sure the problem is a parser problem. (If you are not sure, search for the issue in eslint-plugin-svelte repo and open the issue in eslint-plugin-svelte repo if there is no solution.
• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.

What version of ESLint are you using?

8.23.0

What version of eslint-plugin-svelte and svelte-eslint-parser are you using?

• [email protected]
• [email protected]

What did you do?

Configuration

tsconfig.json
{
  "extends": "@tsconfig/svelte/tsconfig.json",
  "compilerOptions": {
    "target": "ESNext",
    "useDefineForClassFields": true,
    "module": "ESNext",
    "resolveJsonModule": true,
    "baseUrl": ".",
    /**
     * Typecheck JS in `.svelte` and `.js` files by default.
     * Disable checkJs if you'd like to use dynamic types in JS.
     * Note that setting allowJs false does not prevent the use
     * of JS in `.svelte` files.
     */
    "allowJs": true,
    "checkJs": true,
    "isolatedModules": true,
    "strict": true
  },
  "include": ["src/**/*.d.ts", "src/**/*.ts", "src/**/*.js", "src/**/*.svelte"],
  "references": [{ "path": "./tsconfig.node.json" }]
}
.eslintrc.js
module.exports = {
  parser: '@typescript-eslint/parser',
  env: {
    es6: true,
    browser: true,
  },
  parserOptions: {
    tsconfigRootDir: __dirname,
    project: ['./tsconfig.json'],
    extraFileExtensions: ['.svelte'],
    parser: '@typescript-eslint/parser',
  },
  plugins: ['@typescript-eslint', 'import'],
  ignorePatterns: [
    'node_modules',
    '.eslintrc.js',
    '*.config.js',
    '*.config.ts',
  ],
  extends: [
    'eslint:recommended',
    'plugin:svelte/recommended',
    'plugin:@typescript-eslint/recommended',
    'plugin:@typescript-eslint/recommended-requiring-type-checking',
  ],
  overrides: [
    {
      files: ['*.svelte'],
      parser: 'svelte-eslint-parser',
      parserOptions: {
        parser: '@typescript-eslint/parser',
      },
    },
  ],
  settings: {
    'import/resolver': {
      typescript: {},
    },
  },
};

<script lang="ts">
import type { EventInfo } from './types'
let info: EventInfo | null = null

const lightFormat = (i: Date | number) => i.toString()

fetch('/fakeurl').then(() => { info = { start_at: 0 } }).catch(console.error)

$: startDate = (info?.start_at ? lightFormat(info.start_at) : null)
const endDate = () => (info?.start_at ? lightFormat(info.start_at) : null)
</script>
 
<input type='text'/>

What did you expect to happen?

No lint error.

What actually happened?

Get Unsafe argument of type anyassigned to a parameter of typenumber | Date``

Link to Minimal Reproducible Example

https://stackblitz.com/edit/vitejs-vite-up2dfg?file=src/App.svelte

Additional comments

only happen when strict: true in tsconfig.json and plugin:@typescript-eslint/recommended-requiring-type-checking in .eslintrc.js

[ota-meshi]

Thank you for this report.

I've found the cause, but haven't found a workaround yet...

info seems to be treated as never in $: scope.

https://typescript-eslint.io/play/#ts=4.8.3&sourceType=module&code=JYOwLgpgTgZghgYwgAgKIDcLgJIhge2QG8AoZZAZzDijAH04wAuZEAVwFsAjaZAH1ZsANkIDcJAL4khEMMlAEWGLGFwF+gkcgC8moSRIJ8IKsiHAA5gAswAMXxQOjHcgAUwFgBFGKAe27QAJQ6AHzyAHRg+ADKYFCgFq6BBjCyCFauAOQA9PAA1hBsUEKZgZFWWK5JocTyeIS6RJTUtAzMyAAMyBLdZQiM6a5GJvgy4dBQDsnSss00YN6Q4gAkLFTziyi6CoQAZLt1BOHrrc4A-GaWNvaOjO71xy30jMEs7CLiQA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tieQEMAZolp9oAc1gBbRC3RRE0aB2iRwYAL4h1QA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA