Dataloader infers wrong type from load method when returning non-base errors

[hayes]

The typing for the load method is not ideal, it basically is typed as load: (some args) => MaybePromse<Error | Shape> where Shape a generic without any constraints. This means if load returns Promise<User | Error> Shape is inferred as being User. The better way to handle this would be to have load be defined as something like load: (some args) => MaybePromse<LoadResult> and then other places that use Shape would be updated to do something like ShapeFromLoadResult<LoadResult> instead of Shape. ShapeFromLoadResult would probably be something like type ShapeFromLoadResult<T> = T extends Error ? never : T