Parameter decorators can't be used on class assigned to variables or constants

[ericmorand]

Consider the following code sample:

const Decorator = () => {
    return (target: object, key: string | symbol, index?: number) => {

    }
}

const Foo = class {
    constructor(@Decorator() foo: string) {

    }
}

const Foo1 = class Foo1 {
    constructor(@Decorator() foo: string) {

    }
}

class Bar {
    constructor(@Decorator() foo: string) {

    }
}

🙁 Actual behavior

TypeScript fails at compiling this code and throws the following compilation error for Foo and Foo1 classes:

error TS1206: Decorators are not valid here.

Class Bar compiles successfully.

🙂 Expected behavior

Since

class Foo {

}

and

const Foo = class {

}

are equivalent syntaxes in ES6, using parameter decorators should be allowed for these two syntaxes.

[ericmorand]

To give a bit of context, allowing parameter decorators for anonymous classes would permit writing things like this in nestjs:

@Module({
    providers: [{
        provide: CatsService,
        useClass: class {
            constructor(@Inject(MyService) private readonly myService: MyServiceInterface) {
            }
        }
    }, MyService],
})
export class AppModule {
}

Instead of having to declare the class first and then assign it to useClass.

[RyanCavanaugh]

Duplicate #7342

[ericmorand]

Sorry about that. I close.