Implement Every Interface

[TonyValenti]

It would be nice if I could do the following:

public class Foo : IEnumerable<T> {
   public IEnumerator<T> GetEnumerator<T>(){
      //....
   }
}

With something like this, GetEnumerator would be implemented for every T.

[CyrusNajmabadi]

I don't know what this is asking for.

[franchyd]

I think he wants a non-generic type to be enumerable as any type ._. I can't fathom as to why though.

[Pretasoc]

With something like this, GetEnumerator would be implemented for every T.

Looks like Extension everithing or shapes to me

[CyrusNajmabadi]

I think he wants a non-generic type to be enumerable as any type

Ah, got it. I'm not sure what this means at all either. :)

[yaakov-h]

If I'm interpreting this correctly...

Currently a generic interface requires the implementing class either be generic itself (class Foo<T> : IBar<T>, or implement a specific variant (class Foo<Baz> : IBar<Baz>).

What you're suggesting is that a non-generic class can implement a generic interface for any T by providing generic methods that match those defined on the interface.

So in your example, I could cast Foo to IEnumerable<int> and GetEnumerator<int> would be called, but if I cast it to IEnumerable<string> then GetEnumerator<string> would be called.

Is that correct?

[TonyValenti]

@yaakov-h Yes! That is correct!

[CyrusNajmabadi]

could you do it like so:

class WhateverFactory
{
  public static IEnumerable<T> Make<T>() => new Whatever<T>();

  private class Whatever<T> : IEnumerable<T> { ... your impl ... } 
}

Also, @TonyValenti can you explain the use case where you want this? The request is too isolated from a real use case, so i don't know why you'd want this.

[CyrusNajmabadi]

@yaakov-h Yes! That is correct!

So how would that actually work? How will you actually provide the stream of integers if someone casts to IEnumerable<int> or the stream of strings if they cast to IEnumerable<string>?

Honestly curious here. Could you show what your implementation of GetEnumerator would be in your original post?

[brabebhin]

Arguably, this could be useful when dealing with numeric collections, which can be converted rather easily in between types (int to double to uint to string to etc).

[franchyd]

@mcosmin222 That sounds more like #110 #1711 or #2038 . A completely unconstrained setup would not lend well to assuming its a numeric type.

[brabebhin]

Obviously op did not clearly state their purposes, but imo this is what they want. It is obviously reasonable to only do the cast between types which are convertible - maybe by overriding the explicit conversion operator.