Implement System Interfaces

[ds5678]

For example, Il2CppSystem.IDisposable is redundant. It should be removed, and all its uses should be replaced with System.IDisposable. Obviously, only a subset of interfaces are suitable for removal.

Requires #142

[ds5678]

Alternatively, we just ensure that interop types implement both the Il2Cpp interface and the System interface.

[Dwedit]

I was thinking about this issue.

For a class like IL2Cpp.System.Collections.Generic.List<T>, it will implement the interop interfaces IList<T>, ICollection<T>, IReadOnlyList<T>, IEnumerable<T>, IReadOnlyCollection<T>, as well as the non-generic interop interfaces IList, ICollection, and IEnumerable.

Ideally you want the interop interfaces to also implement the native interface as well. There's just one little problem, and that's the CopyTo method found in ICollection<T>. It takes in a native array T[].
This is not a problem for the Interop interface, where CopyTo takes in an Il2CppArrayBase<T> object instead.
But when you want to implement the managed-side interface, you need to pass in a native array. This means you need a function to marshal between a native array and a temporary Il2CppArrayBase<T> object.
Normally, this would mean allocating a temporary interop array, copying everything from the native array to the temporary array, calling the function, then copying everything from the temporary array back to the native array.
But CopyTo is pretty specific about what it does. It is write-only, and never reads what's in the array, so there is no need to copy anything in. The temporary array only needs to cover the Count of the collection, and nothing else, so your arrayIndex parameter becomes 0 before it is copied back.

There's also the non-generic ICollection interface which takes in a System.Array. That also need to be marshaled.

[ds5678]

@Dwedit Have you seen my rewrite branch? My goal for this issue is to implement all public System interfaces on the corresponding Il2Cpp interfaces automatically without special casing any important interfaces.

namespace Il2CppSystem.Collections.Generic;

public interface ICollection<T>
{
    void CopyTo(Il2CppArrayBase<T> array, Int32 arrayIndex);
    void System.Collections.Generic.ICollection<T>.CopyTo(T[] array, int arrayIndex)
    {
        Il2CppArrayBase<T> temp = (Il2CppArrayBase<T>)array;
        this.CopyTo(temp, (Int32)arrayIndex);
        temp.CopyTo(array, 0);
    }
}

In the event that method parameters cannot be automatically marshalled (eg SomeClass), the interface will still be implemented.

void IFoo.Bar(SomeClass parameter)
{
    throw new NotSupportedException();
}