Have hover tooltips show instantiated / computed types when selection is multiple characters

Suggestion

🔍 Search Terms

intellisense hover type debugging selection

✅ 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

Under the following conditions:

• An area of code is selected (>=1 characters)
• The selection is a single node in the AST, ignoring whitespace
• The user has triggered a hover within that selection

…can the language service report the computed type of the selected node, either instead of or in addition to the normal hover info?

📃 Motivating Example

I don’t know of a way to get language services to show what MyA<OtherType> computes to in this Playground example with nested type generics.

The next best strategy is to make intermediate types and/or variables to debug though. It’s kind of a pain.

💻 Use Cases

This Tweet inspired by looking at @markerikson’s talk about complex Redux-area types being annoying to debug through 😄. https://twitter.com/JoshuaKGoldberg/status/1520079650055204866

[itamark]

I’m some person on the internet and I third this idea.

[markerikson]

I’m Mark Erikson, and I approve and second this idea 😃