Need a dummy overload to improve inference

TypeScript Version: 3.x, 4.0.0-beta, nightly

Search Terms: dummy fake overload infer

Code

class FieldEvent<T extends Field> {
    constructor(readonly field: T, readonly message: string) { }
}

class Field {
    listen<T extends FieldEvent<Field>>(type: new (...args: any[]) => T, listener: (event: T) => void): void { }
}

class BeforeSetEvent<T extends number | string> extends FieldEvent<ValueField<T>> {
    constructor(field: ValueField<T>, public newValue: T) { super(field, ""); }
}

class AfterSetEvent<T extends number | string> extends FieldEvent<ValueField<T>> {
    constructor(field: ValueField<T>, readonly oldValue: T) { super(field, ""); }
}

class ValueField<T extends number | string> extends Field {
    constructor(public value: T) { super(); }

    // listen<U extends FieldEvent<Field>>(type: new (arg: this) => U, listener: (event: U) => void): void;
    // listen<U extends FieldEvent<Field>>(type: new (...args: any[]) => U, listener: (event: U) => void): void;
    listen<U extends FieldEvent<Field>>(type: new (...args: any[]) => U, listener: (event: U) => void): void {
        super.listen(type, listener);
    }
}

let field = new ValueField(0);
field.listen(FieldEvent, (event) => event.field);                           // event: FieldEvent<any>
field.listen(BeforeSetEvent, (event) => { event.field; event.newValue; });  // event: BeforeSetEvent<any>
field.listen(AfterSetEvent, (event) => { event.field; event.oldValue; });   // event: AfterSetEvent<any>

Expected behavior:
event to be better inferred than any.

Actual behavior:
event inferred as any.

But if we uncomment the 2 overloads, then event is correctly inferred:

field.listen(FieldEvent, (event) => event.field);                           // event: FieldEvent<ValueField<0>>
field.listen(BeforeSetEvent, (event) => { event.field; event.newValue; });  // event: BeforeSetEvent<0>
field.listen(AfterSetEvent, (event) => { event.field; event.oldValue; });   // event: AfterSetEvent<0>

What's surprising (so the reason I consider it as a bug):

• The 1st overload doesn't match any signature.
• But it influences the way the other overload is inferred.

Note that if we replace (arg: this) by () or another type, then:

field.listen(FieldEvent, (event) => event.field);                           // event: FieldEvent<Field>
field.listen(BeforeSetEvent, (event) => { event.field; event.newValue; });  // event: BeforeSetEvent<string | number>
field.listen(AfterSetEvent, (event) => { event.field; event.oldValue; });   // event: AfterSetEvent<string | number>

Playground Link: Playground Link

Related Issues: I first posted #36226 but was not able to solve my issue, until I found the (arg: this) trick.

Bắt đầu bằng cách tái hiện ví dụ trong TypeScript Playground được liên kết, so sánh việc suy luận khi có và không có hai overload. Theo dõi hành vi suy luận generic và phân giải overload của compiler đối với các lệnh gọi listen; hoàn thành khi các callback suy luận ra FieldEvent, BeforeSetEvent và AfterSetEvent cùng các kiểu cụ thể tương ứng mà không cần các overload giả.