microsoft / microsoft/TypeScript
Can't use async arrow function in/before super call
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Seit 05.2.2021.
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Beschreibung
Bug Report
🔎 Search Terms
super async arrow function this
🕗 Version & Regression Information
This only occurs using a target version of ES2016 or lower.
⏯ Playground Link
💻 Code
This works:
class A {
constructor(fn: () => Promise<void>) {
fn();
}
}
class B extends A {
constructor() {
super(async function () {
console.log("Hello");
});
}
}
new B();
This doesn't:
class A {
constructor(fn: () => Promise<void>) {
fn();
}
}
class B extends A {
constructor() {
super(async () => {
console.log("Hello");
});
}
}
new B();
The difference between the examples is the use of an arrow function vs a traditional function.
🙁 Actual behavior
It compiles crashes however at runtime with this error message:
ReferenceError: Must call super constructor in derived class before accessing 'this' or returning from derived constructor
The error lies in the generated __awaiter function trying to access this. The traditional function wraps the __awaiter call (therefore binding its own this) not causing it to fail.
🙂 Expected behavior
Print Hello to the console.
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