Property 'X' does not exist on type Y

Bug Report

🔎 Search Terms

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about "does not exist on type"

⏯ Playground Link

Playground link with relevant code

💻 Code

type Listener = {
    callback(): boolean;
};

const fn = <T extends Listener>(listener: T) => { };

// this works
fn({
    context: new Map<string, number>(),
    callback() {
        const num = this.context.get('number') ?? 0;

        if (num > 0) return true;
        else return false;
    },
});

// this does not
fn({
    context: new Map<string, number>(),
    callback() {
        const num = this.context.get('number') ?? 0; // Property 'context' does not exist on type 'Listener'.(2339)
        return num > 0;
    },
});

🙁 Actual behavior

It is giving a compilation error as soon as I change the return variable.

🙂 Expected behavior

Should not give compilation errors.

Start with the linked TypeScript Playground example and compare the two calls to fn, focusing on contextual typing and generic inference for the callback's this value. The issue is done when the second example compiles without the reported Property 'context' error while preserving the behavior of the first example.