Set context of this keyword in definition file

Search Terms

set this context in typescript definition file

Suggestion

A way to change the context of this keyword in a type definition file. This is admittedly a weird feature since, to my knowledge, it doesn't really align with how modules work. Perhaps there is another way to achieve this use case.

Use Cases

Here's a video of how my application works - https://vimeo.com/315553984

I have an application that allows users to write code which will then be executed via the Function API - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function
Here's a simplified version of how the app works at its core -

const userCode = `
  console.log(this, foo, bar);
`;
const func = Function('foo', 'bar', userCode);
func.call({myThis: 'hello'}, 'fooString', 'barString');

My app allows users to write their code in Monaco editor and I've successfully added type definitions for the foo and bar variables via the addExtraLib method - https://microsoft.github.io/monaco-editor/api/interfaces/monaco.languages.typescript.languageservicedefaults.html

So when the user starts to type foo intellisense informs them that it is a string. I'd like to do the same for the this keyword.

Examples

See use cases ^

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Start by reviewing how TypeScript definition files represent the this keyword and how that information reaches Monaco's addExtraLib language service. Use the Function API example as the target use case, and verify that editor IntelliSense can infer the requested this context without changing JavaScript runtime behavior.