Debug: ESLint 'Parsing error: Unexpected token' with TypeScript

ESLint throws parsing errors on TypeScript syntax (type annotations, interfaces, generics) even though TypeScript compiles fine.

ESLint needs a TypeScript parser:

1. For ESLint v9+ (flat config):

npm install -D typescript-eslint

// eslint.config.js
import tseslint from 'typescript-eslint';
export default tseslint.config(
...tseslint.configs.recommended,
);

1. For ESLint v8 (.eslintrc):

npm install -D @typescript-eslint/parser @typescript-eslint/eslint-plugin

// .eslintrc.json
{
"parser": "@typescript-eslint/parser",
"plugins": ["@typescript-eslint"],
"extends": ["plugin:@typescript-eslint/recommended"]
}

1. If using project references (tsconfig.json):

{
"parserOptions": {
"project": "./tsconfig.json"
}
}

1. Common fix: ensure file is included in tsconfig:

// tsconfig.json
{ "include": ["src//", "tests//"] }

1. VSCode: restart ESLint server after config changes:

Cmd+Shift+P > ESLint: Restart ESLint Server