Registering Generic Types

[Vennotius]

When registering a generic type "incorrectly", there is some code in ReferenceType's constructor that looks like it wants to correct the registration (for example MyType<string, object> will become MyType<,>). But after doing that, an exception is thrown. I admit to not understanding this behaviour. :sweat_smile:

public ReferenceType(string name, Type type)
{
    if (string.IsNullOrWhiteSpace(name))
        throw new ArgumentNullException(nameof(name));

    if (type == null)
        throw new ArgumentNullException(nameof(type));

    if (type.IsGenericType && !type.IsGenericTypeDefinition)
    {
        var genericType = type.GetGenericTypeDefinition();
        var genericTypeName = genericType.Name.Substring(0, genericType.Name.IndexOf('`'));
        genericTypeName += $"<{new string(',', genericType.GetGenericArguments().Length - 1)}>";
        throw new ArgumentException($"Generic type must be referenced via its generic definition: {genericTypeName}");
    }

    Type = type;
    Name = name;
    ExtensionMethods = ReflectionExtensions.GetExtensionMethods(type).ToList();
}

Would it not be in line with the code's intention to not throw the exception?

public ReferenceType(string name, Type type)
{
    if (string.IsNullOrWhiteSpace(name))
        throw new ArgumentNullException(nameof(name));

    if (type == null)
        throw new ArgumentNullException(nameof(type));

    if (type.IsGenericType && !type.IsGenericTypeDefinition)
    {
        var genericType = type.GetGenericTypeDefinition();
        var genericTypeName = genericType.Name.Substring(0, genericType.Name.IndexOf('`'));
        genericTypeName += $"<{new string(',', genericType.GetGenericArguments().Length - 1)}>";
        Type = genericType;
        Name = genericTypeName;
    }
    else
    {
        Type = type;
        Name = name;
    }
    ExtensionMethods = ReflectionExtensions.GetExtensionMethods(Type).ToList();
}

I ran into this because I was trying to register my type correctly, but got an error, and had to register it as a closed type. public class Cache<TKey, TValue> yells at me when i register it like this Reference(typeof(Cache<>)):

Error CS0305 Using the generic type 'Cache<TKey, TValue>' requires 2 type arguments

---

I have looked at #264 and https://github.com/dynamicexpresso/DynamicExpresso/pull/268, but I am not any wiser.

[metoule]

The idea was to have an explicit error message, to help the user register the expected type. For example, Register(typeof(Cache<,>)). We could automatically change the registration to the generic definition instead of throwing, but that would silently hide the fact that it's not the closed type that must be registered.

[Vennotius]

I understand. Thank you. I guess this code is there just for reference if someone wanted to use it.

var genericType = type.GetGenericTypeDefinition();
var genericTypeName = genericType.Name.Substring(0, genericType.Name.IndexOf('`'));
genericTypeName += $"<{new string(',', genericType.GetGenericArguments().Length - 1)}>";