Multidimensional readonly arrays

Search Terms

readonly array multi multidimensional

Suggestion

The readonly modifier should work with multidimensional arrays.

Use Cases

I assumed readonly number[][] to be multidimensional array which is readonly, but it translates to ReadonlyArray<number[]>, this feels like a footgun.

It is currently also not very intuitive which array is readonly: ReadonlyArray<number>[] or ReadonlyArray<number[]>, without trying it out.

Examples

I'd expect readonly number[][] to be equal to ReadonlyArray<ReadonlyArray<number>>

Explicitely "mixed mutable" arrays could be achieved using parens:

(readonly number[])[] == ReadonlyArray<number>[]
readonly (number[])[] == ReadonlyArray<number[]>

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, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Beginnen Sie mit der Prüfung der vorgeschlagenen Bedeutungen für readonly number[][], ReadonlyArray<number>[] und ReadonlyArray<number[]> sowie der eingeklammerten Alternativen. Bestimmen Sie, ob die angeforderte Kurzschreibweise konsistent spezifiziert werden kann, ohne bestehenden Code zu ändern, und dokumentieren Sie anschließend die akzeptierten Semantiken und validieren Sie sie anhand der aufgeführten Beispiele.