C#•3y ago

❔ Covariant Interface Return

Is there some reason why this doesn't work? I understand we can get this behavior with virtual methods and inheritance, but it feels like this should work with interfaces.

interface IFooReturner { Foo GetFoo(); }
class Foo {}
class FooBar : Foo {}
class FooBarGetter : IFooReturner { FooBar GetFoo(); }

interface IFooReturner { Foo GetFoo(); }
class Foo {}
class FooBar : Foo {}
class FooBarGetter : IFooReturner { FooBar GetFoo(); }

interface IFooReturner { Foo GetFoo(); }
class Foo {}
class FooBar : Foo {}
class FooBarGetter : IFooReturner { FooBar GetFoo(); }

interface IFooReturner { Foo GetFoo(); }
class Foo {}
class FooBar : Foo {}
class FooBarGetter : IFooReturner { FooBar GetFoo(); }

If FooBar is a Foo, this implementation should be valid no?

❔ Covariant Interface Return

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