Allow specifying diagnostic code in ts-expect-error

Suggestion

🔍 Search Terms

ts-expect-error

✅ Viability 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, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

Allow @ts-expect-error to specify diagnostic codes to be more precise in expectations.
Example:
// @ts-expect-error TS1234

Will only expect that diagnostic code. If the same line triggers a different diagnostic code, the expectation will error as if there was no error on the proceeding line.

📃 Motivating Example

This feature will be particularly useful when migrating code (1) between repositories with different TS configs, or even for (2) a slightly safer path when upgrading TS versions if all issues are not immediately fixed.

💻 Use Cases

The Teams Org is facing a code migration that I expect will benefit from this greatly. Please reach out to me (or I will come to office hours) and we can go through that example.

Code

I have attached a PR which implements the change as an example. Let me know what you think!

Start by reviewing the attached example PR and the existing @ts-expect-error behavior described in the issue. Confirm how a diagnostic code should be parsed and matched, then add coverage showing that the expected code is accepted while a different or missing diagnostic causes an error.