[no-use-before-define] False positive on type guard cast

[RebeccaStevens]

• 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

{
  "rules": {
    "@typescript-eslint/no-use-before-define": "error"
  }
}

import { isNumber } from 'type-guards';
type Id = number;

const isId = isNumber as (value: unknown) => value is Id;

Expected Result

No error, value is part of the type, it's not being "used".

Actual Result

const isId = isNumber as (value: unknown) => value is Id;
//                                           ~~~~~ 'value' was used before it was defined. (eslint@typescript-eslint/no-use-before-define)

Additional Info

Versions

package	version
@typescript-eslint/eslint-plugin	4.1.0
@typescript-eslint/parser	4.1.0
TypeScript	4.0.2
ESLint	7.2.0
node	12.18.1

[bradzacher]

This is a fun bug because technically (value: unknown) creates a "value" variable in the function type's scope (x is y and typeof x both require that x is a "value" variable, not a "type" variable).

So the rule is seeing a "value" variable with no initialisation and reporting. Should be a pretty easy fix.