Incorrect errors when adding `this` parameter to functions

[olee]

Bug Report

• TSLint version: (unknown - tslint used by Atom plugin linter-tslint)
• TypeScript version: latest
• Running TSLint via: Atom

TypeScript code being linted

function cloneEntity(this: IEntity) {
    var result = Object.create(Object.getPrototypeOf(this));
    Object.keys(this).filter(key => !key.startsWith('$') && filteredEntityProperties.indexOf(key) < 0).forEach((key) => {
        result[key] = angular.copy(this[key]);
    });
    return result;
}

Actual behavior

The following errors are show (in Atom)

no-unused-expression - expected an assignment or function callat line 22 col 22
no-unused-expression - expected an assignment or function callat line 22 col 28
semicolon - missing semicolonat line 22 col 26
semicolon - missing semicolonat line 22 col 35

Expected behavior

No error shown

[adidahiya]

Can you please dig in and find the tslint & typescript version actually in use? By "latest" do you mean v2.0? I think this has to do with some new syntax introduced recently into the language.

[olee]

The definition of a this type in functions was added in this PR and it is part of Typescript 2.0
I think tslint probably just doesn't support it yet.

[olee]

Do you still need more information?
I don't really know what else I could provide you.
It would be really nice if tslint could handle those cases because right now I get warnings everywhere...

[adidahiya]

@olee have you tryied using tslint@next? See this bit of the readme about using latest versions of the compiler: https://github.com/palantir/tslint#peer-dependencies

[olee]

How would I go about using tslint@next in Atom-typescript so I can try it?
Does someone know that?

[jkillian]

You could try npm install -g tslint@next and try running it on your code via the CLI. If you can duplicate the bug via the CLI, it's definitely a TSLint bug

[olee]

Indeed, using tslint together with typescript@next seems to work properly with this test code:

function formatShortDate(this: Date) {
    return `${this.getFullYear()}-${this.getMonth()}-${this.getDate()}`;
}

Date.prototype.formatShortDate = formatShortDate;

console.log(new Date().formatShortDate());

Now I just need to figure out how to get atom-tslint to use typescript@next (or tslint@next) as well...

EDIT: Seems that linter-tslint allows using different tslint version, however right now it crashes when loading new typescript version so that needs to be fixed first: AtomLinter/linter-tslint#104

[jkillian]

Glad it's not a TSLInt bug! Going to close this issue, but feel free to continue discussion here if needed