Report evolving arrays / evolving variables differently in QuickInfo

Suggestion

🔍 Search Terms

evolving array any quickinfo tooltip

✅ 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

When hovering over an evolving array, we should show the type as something special so that people don't think it's actually any and get mad/confused about it

Proposed
Instead of

const arr = [];
arr
// ?^ any[]

show

const arr = [];
arr
// ?^ (evolving array)

Same for

let a;

📃 Motivating Example

We have many reports both external and internal of people thinking that an evolving array is of type any. This also appears as bug reports where people think that noImplicitAny has a bug in it because it's not reporting one

Recently https://twitter.com/mattpocockuk/status/1662103198910300161

#43752
#45369

💻 Use Cases

Prevent confusion

Start by tracing the TypeScript QuickInfo path for evolving arrays and uninitialized variables, then review the related discussions in issues #43752 and #45369. Done means hover information distinguishes evolving arrays and evolving variables from ordinary any types without changing runtime behavior.