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Support readonly types with inference #32812
Description
Search Terms
readonly without type
Suggestion
Today, in order to use a readonly type with inference you need to know typeof exists
const user = {
name: "orta"
}
const readonlyUsers: readonly typeof user[] = [user] It would be nice to support shorthand syntax for this:
const user = {
name: "orta"
}
const readonlyUsers: readonly = [user] Where the lack of a definition outside of readonly implies you want to keep the inferred type.
Use Cases
Making it cheaper syntactically to use readonly more often without using slightly more esoteric typescript features.
Could be negated by these though:
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.
Activity
RyanCavanaugh commentedon Aug 12, 2019
Can you compare and contrast with how
as constdoesn't address this use case?jack-williams commentedon Aug 13, 2019
From the PR that added
readonly(#29435) there was a question about the behaviour of types calledreadonlyhere. The following used to compile, but does not currently:I think there was a plan to fix this, but maybe though would need to be reviewed in light of this proposal.
orta commentedon Aug 13, 2019
Hrm great point - I actually can't think of any reason why
as constdoesn't cover this other than for the exact case I was looking at (which was to show a particular error message )I'm fine with this being considered closed 👍
RyanCavanaugh commentedon Aug 14, 2019
As an aside I think we're happy with
readonlybeing (unintentionally?) reserved for the time being - who knows what we might want with it later.