Wrong error message for `this` in function

TypeScript Version: 3.1.0-dev.20180810

Code

function f() {
    this.x;
}

Expected behavior:

Error that this is implicitly any.

Actual behavior:

src/a.ts:2:5 - error TS7041: The containing arrow function captures the global value of 'this' which implicitly has type 'any'.

...what arrow function?
(Ref: #25978)

On that note, we should also have a good error message in the following situation:

class C {
    m() {
        this.m();
        function f() {
            this.m();
        }
    }
}

This is a common error and it's not obvious why this works in one place but not the other. The error message should indicate the place where this was shadowed.

[nermin99]

How do you disable this rule?