为何触发TypeScript ESLint的@typescript-eslint/no-unnecessary-condition错误？

最近从JavaScript转用TypeScript，遇到TypeScript ESLint抛出**"Unnecessary conditional, value is always truthy"**错误（对应规则@typescript-eslint/no-unnecessary-condition）。错误触发场景很奇怪，不仅出现在条件语句中，甚至像let diff = (oldIndent - newIndent) / 2这种普通赋值代码也会报错。关闭并重新打开文件后，红色波浪线依然存在，且错误出现在多个随机位置。

错误示例截图 #

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项目配置文件 #

.prettierrc

{
  "semi": false,
  "trailingComma": "all",
  "singleQuote": true,
  "printWidth": 64,
  "tabWidth": 2,
  "useTabs": false,
  "arrowParens": "avoid",
  "quoteProps": "as-needed",
  "bracketSpacing": true,
  "proseWrap": "always",
  "endOfLine": "lf",
  "singleAttributePerLine": true,
  "prettierPath": "./node_modules/prettier"
}

tsconfig.json

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es2020",
    "lib": ["es2020"],
    "outDir": "host",
    "rootDir": "make",
    "sourceMap": true,
    "strictNullChecks": true
  },
  "include": ["make"],
  "exclude": ["node_modules"]
}

.eslintrc.json

{
  "env": {
    "browser": true,
    "es2021": true
  },
  "parserOptions": {
    "ecmaVersion": "latest",
    "sourceType": "module",
    "project": ["./tsconfig.json"]
  },
  "parser": "@typescript-eslint/parser",
  "plugins": ["@typescript-eslint"],
  "extends": [],
  "rules": {
    "curly": 2,
    "brace-style": ["error", "1tbs"],
    "@typescript-eslint/quotes": [
      "error",
      "single",
      {
        "avoidEscape": true,
        "allowTemplateLiterals": true
      }
    ],
    "@typescript-eslint/no-unnecessary-condition": {
      "allowConstantLoopConditions": true
    }
  }
}

.vscode/settings.json

{
  "editor.defaultFormatter": "esbenp.prettier-vscode",
  "editor.formatOnSave": true,
  "eslint.format.enable": true,
  "editor.codeActionsOnSave": {
    "source.fixAll.eslint": true
  },
  "eslint.validate": ["javascript", "typescript"],
  "eslint.nodePath": "./node_modules/eslint",
  "eslint.packageManager": "npm"
}

想问下这种错误是什么原因导致的？是我哪里配置或代码写错了，还是TypeScript ESLint的Bug？

内容的提问来源于stack exchange，提问作者Lance Pollard