Factory extension silently binds Func<...>

[l3m]

In our code, we had a really weird bug related to Ninject, and according to this stackoverflow answer, the root cause was that the Ninject Factory extension bind Func<T,T,bool> (and possibly other Funcs).

Assume an object such as

public class PriorityQueue<T>(Func<T,T,bool> cmp_func) : IPriorityQueue<T>
{ ... } 

and a Factory

public IPriorityQueueFactory 
{
    IPriorityQueue<T> Create<T>();
} 

The expected behavior would be that Ninject will throw an exception, because the constructor argument was not bound. But this will not happen; instead, the factory extension will silently inject the non-user-bound Func<...>.

This is very confusing, and it cost me a long time to track down the bug.

I would assume that for most users, silently adding bindings for something as common as a Func<...> is outside of the expected behavior of a ninject extension.

The problem gets even worse if using custom factories as explained here. Then the bug occurs if the factory extension is in the usings, but behaves correctly otherwise.