Allow customization of type display format in hover tooltips

🔍 Search Terms

• customization type display
• Array or T[]

✅ Viability Checklist

• 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 isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

In TypeScript, when hovering over a variable, the inferred type is displayed in a specific format.
For instance, an array of numbers is shown as number[].
However, some developers, including myself, prefer the alternative format Array<number> for readability and consistency with other generic types.

📃 Motivating Example

I have noticed that there is an WriteArrayAsGenericType flag in the Abstract Syntax Tree (AST) that can convert T[] to Array<T>.

I would like to request the addition of a configuration option in tsconfig.json to enable this flag, allowing developers to choose their preferred format for array types in hover tooltips.

For example:

{
  "compilerOptions": {
    "typeDisplayFormat": "generic" // Options could be "generic" for Array<number> or "shorthand" for number[]
  }
}

💻 Use Cases

Complex Type Readability: I frequently write functional code that can lead to complex types like Task<Maybe<Task<Maybe<T[]>>[]>>[]. The shorthand [] notation can make it difficult to understand the nested generic relationships. Displaying these types as Array<T> would significantly improve readability and comprehension.

Consistency: Most other generic types use angle brackets (e.g., Promise<T>, Map<K, V>), and only array types use the special shorthand (number[]). Aligning array types with this convention would ensure consistency across all types and improve clarity.

Start by tracing how hover tooltip types are formatted and where the AST's WriteArrayAsGenericType flag is used. Review how compilerOptions are defined and consumed, then determine the configuration and display behavior needed for generic versus shorthand array types. Done means the selected format appears consistently in hover tooltips without changing emitted JavaScript.