no-invalid-this should allow this in assigned methods

[ghost]

Bug Report

• TSLint version: 3.15.1
• TypeScript version: 2.1.0-dev.2016-0907
• Running TSLint via: gulp

TypeScript code being linted

const systemLocate = System.locate,
    suffix = `?nocache=${Math.random()}`;
System.locate = function( ...args ) {
    return Promise.resolve( systemLocate.apply( this, args ) )
        .then( addr => addr + suffix );
};

with tslint.json configuration:

{
"no-invalid-this": [
            true,
            "check-function-in-method"
        ]
}

Actual behavior

the "this" keyword is disallowed outside of a class body

Expected behavior

No error.

The eslint rule with the same name allows for this references when assigning methods:

obj.foo = function foo() {
    // OK, this is in a method (this function assigns to a property).
    this.a = 0;
};

I would expect this to be valid in TypeScript as well.

Specificying an explicit this parameter does not clear the error. I would consider this an acceptable alternative, if it worked.

[englercj]

Bumped up against this today while doing the following:

MyClass.prototype.method = function () {
    return this.something; // `this` gives a tslint error for no-invalid-this
};

[adidahiya]

we're going to deprecate this rule; do you think you still need it given the compiler option? #1861

[ghost]

No.

[englercj]

I feel like they are different. I'm OK with implicit this when on a class method, but want to disallow this (or more specifically, implicit this) when on a non-class method.

Right now there isn't a way to enforce that with just the compiler option, it is either all explicit or all implicit. Or do I misunderstand the usage?