class Stub
{
}
interface IListener<T>
{
method( e : Event<T> ) : void;
}
class Event<T>
{
target : T;
}
class Listener implements IListener<Stub>
{
method( e : Event<boolean> ) : void
{
}
}
Is there any reason why TS compiler doesn't complain ? 'boolean' violates the interface contract. Stub type is specified in the implementation.
This is because TypeScript is structurally typed. The following works (which is a simplification of your code sample:
class Stub
{
}
let foo:Stub = true; // Allowed ... `boolean` has all the member that a Stub has
However the following will fail:
class Stub
{
someMember: string;
}
let foo:Stub = true; // Error. A boolean doesn't have `someMember` which should exist on a `Stub`
The reason for this is developer convenience.
Here is more discussion : http://basarat.gitbooks.io/typescript/content/docs/why-typescript.html
I guess it is due to the fact your Stub class does not expect anything which is fulfilled by basically every other type (incl. your boolean example). If you add e.g. x:number to your stub it will be flagged as error then.
