`this` incorrectly transformed to `_classThis` in downlevel static `accessor`

[rbuckton]

Bug Report

🔎 Search Terms

static accessor this

🕗 Version & Regression Information

• This is the behavior since ES Decorators were introduced in 5.0

⏯ Playground Link

Playground link with relevant code

💻 Code

// @experimentalDecorators: false
// @target: es2021
@((t, c) => t)
class C {
    static #a = 0;
    static get a() { return this.#a; }
    static set a(v) { this.#a = v; }

    static accessor b = 0;
}

// correctly errors at runtime.
Object.getOwnPropertyDescriptor(C, "a")!.get!.call({});

// correctly errors at runtime.
Object.getOwnPropertyDescriptor(C, "a")!.set!.call({}, 1);

// should error at runtime, but does not.
Object.getOwnPropertyDescriptor(C, "b")!.get!.call({});

// should error at runtime, but does not.
Object.getOwnPropertyDescriptor(C, "b")!.set!.call({}, 1);

🙁 Actual behavior

The emit for static accessor b incorrectly transforms a this into _classThis:

let C = (() => {
    ...
    var C = _classThis = class {
        static get a() { return __classPrivateFieldGet(this, _classThis, "f", _a); }
        static set a(v) { __classPrivateFieldSet(this, _classThis, v, "f", _a); }
        static get b() { return __classPrivateFieldGet(_classThis, _classThis, "f", _b_accessor_storage); }
        static set b(value) { __classPrivateFieldSet(_classThis, _classThis, value, "f", _b_accessor_storage); }
    };
    ...
})();

The result is that the actual this isn't correctly brand-checked.

🙂 Expected behavior

let C = (() => {
    ...
    var C = _classThis = class {
        static get a() { return __classPrivateFieldGet(this, _classThis, "f", _a); }
        static set a(v) { __classPrivateFieldSet(this, _classThis, v, "f", _a); }
        static get b() { return __classPrivateFieldGet(this, _classThis, "f", _b_accessor_storage); }
        static set b(value) { __classPrivateFieldSet(this, _classThis, value, "f", _b_accessor_storage); }
    };
    ...
})();