[no-unused-vars] False positive: type import used in typeof

[DisappearedStar]

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I have read the FAQ and my problem is not listed.

Repro

.eslintrc.js

{
  rules: {
    'no-unused-vars': 'off',
    '@typescript-eslint/no-unused-vars': ['error', {
        varsIgnorePattern: '^_',
        argsIgnorePattern: '^_',
        ignoreRestSiblings: true,
    }],
  }
}

tsconfig.json

{
  "compilerOptions": {
    "module": "esnext",
    "moduleResolution": "node",
    "target": "es5",
    "allowJs": true,
    "importHelpers": true,
    "jsx": "react",
    "experimentalDecorators": true,
    "isolatedModules": true,
    "importsNotUsedAsValues": "error"
  }
}

// a.ts
export const foo = 42;

// b.ts
import type { foo } from './a';

export type Bar = typeof foo;

Expected Result

No lint errors

Actual Result

b.ts 1:15 'foo' is defined but never used. Allowed unused vars must match /^_/u. (@typescript-eslint/no-unused-vars)

Additional Info

Versions

package	version
@typescript-eslint/eslint-plugin	4.0.1
@typescript-eslint/parser	4.0.1
TypeScript	4.0.2
ESLint	7.8.0
node	10.16.3

[bradzacher]

This is stupidly weird and not all what I expect.
I'm really surprised that it works this way.

When I see import type { foo }, I expect that this should either:

1. error, because foo is a value (i.e. you can't import a value as a type)
2. be fine but foo and under the hood TS would treat it the same as typeof foo.

Instead for all intents and purposes, TS treats foo as a value, however it only allows foo be referenced in type contexts.

This breaks the assumption that I'd made that all import types are 100% types.
No biggie - easy fix, it just feels wrong.

[DisappearedStar]

I confirm that the error is fixed in 4.0.2-alpha.9.

[Wolk]

Hi, i am still having this bug in 4.0.3

example of my problem

// file 1
export type FieldDefinition = {
  [key: string]: string[];
};

// file 2
interface FruitsFormDefinition {
  apple: string;
  orange: string;
}

export type FruitsFieldDefinition = { [K in keyof FruitsFormDefinition]: FieldDefinition[string] };

export const fruitsFieldDefiniton: FruitsFieldDefinition = {
  apple: [],
  orange: ['isRequired'],
};

the error i get is
Line 32:37: 'K' is defined but never used. Allowed unused vars must match /^_/u @typescript-eslint/no-unused-vars

[OriginLive]

^ made a new ticket, since it's not directly related #2615