[no-unused-vars] false-positive for class expressions

[ocavue]

• 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

$ git clone https://github.com/ocavue/typescript-eslint-issue-2831 /tmp/eslint-issue
$ cd /tmp/eslint-issue
$ yarn install 
$ yarn run lint 

Thanks for @derekparsons718 and @lukeapage for more examples.

export const arrayWithClasses = [class C1 { }]

export const objectWithClasses = {
    controller: class MyClass { }
}

export const functionReturnsClass = (): unknown => {
    return class A {}
}

Expected Result

No warning.

Actual Result

  1:40  warning  'C1' is defined but never used       @typescript-eslint/no-unused-vars
  4:23  warning  'MyClass' is defined but never used  @typescript-eslint/no-unused-vars
  8:18  warning  'A' is defined but never used        @typescript-eslint/no-unused-vars

Additional Info

If I downgrade @typescript-eslint/eslint-plugin and @typescript-eslint/parser to version 4.8.2, no warning occurs.
Versions

package	version
@typescript-eslint/eslint-plugin	4.9.0
@typescript-eslint/parser	4.9.0
TypeScript	4.1.2
ESLint	7.14.0
node	15.2.1

[bradzacher]

that's an interesting pattern I've never seen before.

[derekparsons718]

I have a very similar case. Only difference is that the class is declared as an object property instead of an array element, and the object is exported for use in other files.

export const objectWithClasses = {
    controller: class MyClass { //warning: 'MyClass' is defined but never used
        //...
    }
}

I assume this is the same problem, but I can open a new issue if desired.

[bradzacher]

@derekparsons718 - yup that's the same issue with class expressions.

[lukeapage]

Assume this is the same too:

const a = () => {
    return class A {};
};

[traverse]

Assume this is the same too:

const a = () => {
    return class A {};
};

Yep that one as well, just ran into that exact issue.

[ocavue]

Just added the examples above into the origin issue description. In case someone else ran into the same cases.

[ocavue]

@bradzacher I can confirm that version 4.9.1 fixes this issue. Thanks for your help.

[lukeapage]

@bradzacher
The example I posted is still broken in 4.9.1. New issue or will you re-open?
#2831 (comment)

[ocavue]

@bradzacher

The example I posted is still broken in 4.9.1. New issue or will you re-open?

#2831 (comment)

That is strange because I run through all the examples (including yours) and it seems to be okay. Can you check your lock files (e.g. yarn.lock) and see if there are two versions of this package?

[bradzacher]

Yup - working fine against master.
You likely have an old version installed.

[lukeapage]

Sorry! I made a mistake and had accidentally reverted the dependabot branch to 2.9.0