[bug] Auto accessor fields are declared as regular properties in mixin abstract classes

[TechQuery]

🔎 Search Terms

abstract class mixin accessor field property declaration .d.ts ts(2611)

🕗 Version & Regression Information

• This changed between versions ______ and _______
• This changed in commit or PR _______
• This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
• I was unable to test this on prior versions because _______

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.8.0-dev.20241203#code/PTAEAMEsDsBMFMAeA6WyAuBncpKdAObzTwBOAhuvLKAEYCeEWAxqALRvwC2k6AIvGYAbchXSQA9tADy0IfRwwIXemyGRaFUgoBQSAA4TS6UAmGj4ocrUzoKzE+cz4AQuUyWA3jtC+rzZnhnIysALlBoAFcuWjIAbh0AXz1EQ2NTQRFSSwAzSOgHSWhQHlhYIXgACgBlSP0yAH5w9Hp6iRzQNw8ASnDrW3sTEgB3UEru0ABeAD5Qbz8wiOjY0gTEhJBcLjSTTxLIMorQRNAc0gkuUAByFTUNLXorhIMjRxFnUAAxGHIhUCQqHB8KVylUJvM-OQAkFMCFyFNQAAmOK+TZYSqIgBsAEZsRMyOdSEkgA

💻 Code

// `index.d.ts` is generated by `tsc --emitDeclarationOnly` in `my-library`
declare abstract class Base {
    accessor a: number;
}
declare function middle(Super?: typeof Base): abstract new () => {
    a: number;
};
// import { middle } from 'my-library';
class Final extends middle() {
    accessor a = 2;  // ts(2611) error
}

🙁 Actual behavior

TS throws:

'a' is defined as a property in class '{ a: number; }', but is overridden here in 'Final' as an accessor. ts(2611)

but the library source code is:

export abstract class Base {
    accessor a = 1;
}

export function middle(Super = Base) {
    abstract class Middle extends Super {
    }
    return Middle;
}

🙂 Expected behavior

It has no type error while overrides auto accessor fields in sub classes of abstract mixins from 3rd-party libraries.

Additional information about the issue

This bug can be resolved if tsc generates .d.ts as shown below:

// `index.d.ts` is generated by `tsc --emitDeclarationOnly` in `my-library`
declare abstract class Base {
    accessor a: number;
}
declare function middle(Super?: typeof Base): abstract new () => {
-    a: number;
+    get a(): number;
+    set a(value: number);
};
// import { middle } from 'my-library';
class Final extends middle() {
    accessor a = 2;  // no error
}

https://www.typescriptlang.org/play/?ts=5.8.0-dev.20241203#code/PTAEAMEsDsBMFMAeA6WyAuBncpKdAObzTwBOAhuvLKAEYCeEWAxqALRvwC2k6AIvGYAbchXSQA9tADy0IfRwwIXemyGRaFUgoBQSAA4TS6UAmGj4ocrUzoKzE+cz4AQuUyWA3jtC+rzZnhnIysALlBoAFcuWjIAbh0AXz1EQ2NTQRFSSwAzSOgHSWhQHlhYIXgACgBlSP0yAH5w9Hp6iRzQNw8ASnDrW3sTEgB3UEru0ABeAD5Qbz9CeBNycfComPifPw9lyoA3ciFI+DXo2NJuhMSEkFwuNJNPEsgyitBE0BzSCS5QAHIVGoNFp6H8EgYjI4RM5QAAxGCHUBIKhwfClcpVCbzPzkAJBTAhchTUAAJjivluWEqJIAbABGOkTMjfUhJIA

[Andarist]

I believe this is related to #44938 and #58790 . They involve intersections though and yours doesnt but ultimately all of them are about accessors serialization

EDIT:// I might have spoken too soon. After further analyzing this and the related issues - the other ones are really just about intersected getters whereas this one is purely about accessors serialization. Note though that it's not exclusive to accessors. Getters and setters are prone to this too: TS playground