disallow abstract property declaration with value in class

[LongTengDao]

Search Terms

Suggestion

abstract class C {
    abstract method () :Type;// valid
    abstract property :Type;// valid
    abstract property :Type = value; // this should be invalid, because it doesn't make sense
}

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Examples

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.

[RyanCavanaugh]

Breaking changeness aside, I don't see by what logic we would disallow it. TS should always let you write

this.property = value;

in a method body. Disallowing you from using the sugar to do that in the constructor body would be entirely arbitrary

[LongTengDao]

@RyanCavanaugh abstract property assignment will always be overriden by sub class, it should not have value assignment behaviour, just like abstract method should not have body block

[RyanCavanaugh]

A child class can have a bare property declaration without an initializer, thus falling back to the parent value.

Either way, we're not interested in taking a breaking change here.

[LongTengDao]

@RyanCavanaugh I see. There is difference between ECMAScript class proposal and TypeScript. In latest proposal, property declaration is define not set, and bare property declaration is equal to = undefined. Now that it's still a proposal, so the breaking problem may be handled together util the proposal be standard.