no-unused-variable-bug

no-unused-variable interferes with other rules palantir/tslint/issues/3455

Bug Report

• TSLint version: 5.8.0
• TypeScript version: 2.6.1
• Running TSLint via: CLI

TypeScript code being linted

import { EventEmitter } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Subject } from 'rxjs/Subject';
import 'rxjs/add/observable/of';
import 'rxjs/add/operator/do';

export const f1 = () => returnsVoid(); // error
export const obs1 = Observable.of(undefined).do(() => returnsVoid()); // error

export class Component {
  subject = new Subject<void>();
  event = new EventEmitter<void>();

  obs2 = Observable.of(undefined).do(() => this.subject.next()); // error
  obs3 = Observable.of(undefined).do(() => this.event.next()); // no error, but should be

  obs4 = Observable.of(undefined).do(this.subject.next); // error
  obs5 = Observable.of(undefined).do(this.event.next); // no error, but should be
}

function returnsVoid() { }

with tslint.json configuration:

{
  "rules": {
    "no-unused-variable": [
      true,
      "check-parameters", {
        "ignore-pattern": "^_"
      }
    ],
    "no-unbound-method": true,
    "no-void-expression": true
  }
}

Actual behavior

When the no-unused-variable variable is enabled, the no-void-expression rule does not report an error on line 15 and the no-unbound-method rule does not report an error on line 18. But if you disable the no-unused-variable rule, the no-void-expression and no-unbound-method rules correctly reports all of the noted errors.

Expected behavior

The no-unused-variable rule should not interfere with other rules.