Enable declarationMap for the typescript project itself

[Andarist]

Suggestion

🔍 Search Terms

source maps, enable, sourcemaps, declarationmap

✅ 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

It would be quite nice if typescript would be shipped with declaration maps. This could help with debugging TS itself.

📃 Motivating Example

Debugging with https://replay.io/ .

💻 Use Cases

I'm currently debugging the inference algorithm to understand it better. However, TS uses a lot of bitmasks, and reading the final code output is not as informative as it could be. TS source code also contains a lot of useful comments that could help during the debugging sessions.

[MartinJohns]

Duplicate of #32207.

[andrewbranch]

Declaration maps (--declarationMap) are source maps from .d.ts files to .ts files, while when we normally talk about “source maps,” we mean source maps from .js files to .ts files (--sourceMap). Which one are you referring to @Andarist?