Typescript: 'declared but never used' for type parameter when there is a broken import

[andy-ms]

TypeScript Version: nightly (2.3.0-dev.20170331)

Code

import { Foo } from "bad-import";

export interface I<T> {
    x: Foo<T>;
}

Expected behavior:

Only an error at the import.

Actual behavior:

src/a.ts(3,20): error TS6133: 'T' is declared but never used.

[andy-ms]

Another case:

import { foo } from "badImport";

type T = number;
foo<T>();

[andy-ms]

Another case:

import { A, B } from "unknown";
export class C extends A<B> {}

B is marked unused.

[kevynb]

Hello, it seems to be fixed on typescript@next. However since this issue can affect users of Typescript v2.2.2 and v2.3 and tslint, would it be possible to ship it in [email protected] instead of 2.4?

[Chris2011]

I have a similar problem: ERROR in ng:///C:/Projekte/groupify/src/app/export/export.component.html (2,1): '$event' is declared but never used.

But the code inside my export.component.html looks like: <button (click)="export()">Export</button>

[Chris2011]

And yes, the error go away after I set noUnusedParameters to false.

[andy-ms]

@Chris2011 I can't really help you without a reproducible code sample. Can you find-all-references on $event to see if you have any uses?

[Chris2011]

I did a full text search. I will have a look later to see where it comes from. I thought it could be the same error here, thats why I jumped in.

[jaredpalmer]

Not sure if this helps anyone, but I solved this "bug" by removing an incorrect spread props {...this.props} in a parent react component.

[juanpablodelatorre]

I'm getting a lot of these in a piece of code that was working fine a couple of days ago. They seem a bit random. One that caught my eye (because it happens again and again in different files) says:

[16:12:52]  tslint: src/pages/detail.ts, line: 4
                  All imports are unused.
       L4:  import { Http } from "@angular/http";

And the relevant code is:

import { Http } from "@angular/http";
export class detail {
    constructor(private http: Http) {}

    pushData(url, payload) {
        this.http.post(url, payload).map(res => res.json()).subscribe(data => console.log(data));
    }
}

Also, this one:

'ErrorHandler' is declared but never used.

import { ErrorHandler } from "@angular/core";
export class MyErrorHandler implements ErrorHandler {
}

I don't know why TSLint started picking these as errors. But it sure started today.

[andy-ms]

@juanpablodelatorre Can you try that out on typescript@next?

[juanpablodelatorre]

@andy-ms Yep, that worked. Thanks!