Preserve `set`-only accessors in declaration emit

リンクされた Playground から始め、same、divergent、readonly、writeonly の各アクセサーについて宣言出力を再現します。オブジェクトアクセサーに対する TypeScript の宣言出力パスを追跡し、既存のアクセサー関連のテストまたはベースラインと比較します。write-only アクセサーが、他に示されている出力を変更せずに、出力された宣言内で保持されれば完了です。

Playground Link

Related to https://github.com/microsoft/TypeScript/issues/58112#issuecomment-2043419380

export let same = {
    set x(value: string) {
    },
    get x(): string {
        throw new Error("Not implemented.")
    },
};

export let divergent = {
    set x(value: string) {
    },
    get x(): number {
        throw new Error("Not implemented.")
    },
};

export let readonly = {
    get x(): string {
        throw new Error("Not implemented.")
    },
};

export let writeonly = {
    set x(value: string) {
    },
};

Current

Notice that in the declaration of writeonly, we don't preserve the accessor at all.

export declare let same: {
    x: string;
};
export declare let divergent: {
    get x(): number;
    set x(value: string);
};
export declare let readonly: {
    readonly x: string;
};
export declare let writeonly: {
    x: string;
};

Expected

If we had a writeonly modifier, I'd argue we could just use that as a parallel to the readonly declaration; however, we do support accessors in declaration emit, and we could emit that in the case of a write-only accessor.

It is technically a breaking change though for consumers of older TypeScript versions, and the only way to opt out would be to declare a no-op get accessor.

export declare let same: {
    x: string;
};
export declare let divergent: {
    get x(): number;
    set x(value: string);
};
export declare let readonly: {
    readonly x: string;
};
export declare let writeonly: {
    set x(): string;
};