Discriminators must implement interfaces that wrapped types are implementing.
To avoid compiler confusion all implementations must be an explicit interface implementations.

API Proposal

The syntax of custom discriminator names

[GeneratedDiscriminatedUnion]
public abstract partial class Result : IDiscriminator<string, Result.Succsess>, IDiscriminator<string, Result.Error>

When generated, if IDiscriminator`2 interface is implemented, second generic argument(not parameter) must be an ErrorTypeSymbol inside the UnionType, so it's name will be taken as Discriminator name. That way, after generation ErrorTypeSymbol would be resolved.

Requirements

• An ability to give custom names to discriminator.
• An analyzer of proper IDiscriminator`2 interface implementation.
• An analyzer of conflicting names (eg: discriminators of same type, discriminators of types of same name from different namespaces, discriminators with same custom name).
• Accomodate changes in ExhaustiveSwitchSuppressor

Discriminators with generic wrapped types must implement all constraint interfaces.

Add checking if type is reference type.

Most of contexts have discriminator information presented by properties:
DiscriminatorName
WrappedTypeSymbol
WrappedTypeName

It should be United in Discriminator type.

If property has an init accessor the set accessor is being generated.

• Make implicit conversion from WrappedType -> DiscriminatorType
• Make implicit conversion from DiscriminatorType -> WrappedType
• Make implicit conversion from WrappedType -> UnionType