microsoft / microsoft/TypeScript
Incorrect emit for parameter properties when using standard class fields
Open
@rbuckton is already working on this.
Since Feb 16, 2024.
Bug
Domain: JS Emit
Rescheduled
- Dominant language
- Go
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Description
Pointed out by @rbuckton on #50971, based on the repro from that bug. When targetting ES2022 or higher, and leaving useDefineWithClassFields: true (the default) for that target:
class Helper {
create(): boolean {
return true
}
}
export class Broken {
constructor(readonly facade: Helper) {
console.log(this.bug)
}
bug = this.facade.create()
}
new Broken(new Helper)
Produces
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.Broken = void 0;
class Helper {
create() {
return true;
}
}
class Broken {
facade;
constructor(facade) {
this.facade = facade;
console.log(this.bug);
}
bug = this.facade.create();
}
exports.Broken = Broken;
new Broken(new Helper);
Currently the compiler issues an error on bug = this.facade.create() to avoid the bad emit, but it might be better to change the emit when parameter properties are used:
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.Broken = void 0;
class Helper {
create() {
return true;
}
}
class Broken {
facade;
bug;
constructor(facade) {
this.facade = facade;
this.bug = this.facade.create();
console.log(this.bug);
}
}
exports.Broken = Broken;
new Broken(new Helper);
Unfortunately, this isn't standard initialisation order for class fields...so it's correct, but not standard. That's probably OK since parameter properties aren't standard.
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