Open
Description
🔍 Search Terms
readonly target library
✅ 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
Read-only variants of ECMAScript interfaces are currently not eligible for script target suggestions. This is most noticeable with ReadonlyArray, since this type can arise through syntax rather than by referencing the symbol directly.
[1,2,3].toReversed();
// ~~~~~~~~~~
// Property 'toReversed' does not exist on type 'number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
([1,2,3] as const).toReversed();
// ~~~~~~~~~~
// Property 'toReversed' does not exist on type 'readonly [1, 2, 3]'.It would be useful if the suggested lib checks could resolve these in the same way.
📃 Motivating Example
As above.
💻 Use Cases
N/A