readme.md

Bug in TSLint no-unused-variable rule.

How to reproduce

If you run tslint -c tslint.json --type-check --project tsconfig.json '*.ts' in this folder you'll see:

$ tslint -c tslint.json --type-check --project tsconfig.json '*.ts'
ERROR: main.ts[1, 1]: All imports are unused.

Conditions

• If you remove any of the files in this project (including fa.ts which is not used at all) the error disappears.
• If you rename fa.ts to something after foo.ts (like h.ts, fz.ts or even fop.ts) the error disappears.
• If you rename fa.ts to something before foo.ts (like a.ts or fon.ts) the error remains
• If you empty fa.ts the error disappears
• If you remove Foo import from main.ts and replace Foo<IBar> for Array<IBar> or Partial<IBar> the error disappears
• And of course if your remove IBar import from main.ts and replace Foo<IBar> for Foo<{}> or something else the error disappears

TSLint version

5.2.0

Typescript version

2.3.2

Discussion

palantir/tslint#2577 (comment)

bar.ts

export interface IBar {
  foo: boolean;
}

fa.ts

import { Foo } from "./foo";

// So we don't have "imports are not used" here
export { Foo };

foo.ts

export class Foo<T> {
  public foo: T;
}

main.ts

import { IBar } from "./bar";
import { Foo } from "./foo";

export function foo(bar: Foo<IBar>) {
  return 1;
}

tsconfig.json

{}

tslint.json

{
  "extends": "tslint:recommended",
  "rules": {
    "no-unused-variable": true
  }
}