Function parameter analyzers

[bcollamore]

See #58 for conversation start.

[bcollamore]

• "In the case of Ints or String parameters, if only 3 values are ever used we can suggest the use of an enum." This idea exposes a limitation of Roslyn: it only works within a project. Therefore, this idea would only benefit for internal or private methods. But it is still interesting and do-able.

• "In the case of methods that is overloaded with types that don't share a hierarchy we can suggest to create an interface."
  This is do-able, and a natural application of Roslyn.

• "We can create a warning for types that have null fields."
  Can you elaborate?

[kryptt]

For the third point,

Its about an alternative approach to https://www.affirmaconsulting.com/null-values-in-c/ in that we look for opportunities to separate a class with optional / null fields into two separate classes that inherit from a base / share an interface.. basically the example used in the article that replaces a big class with a couple of parameters that could be null with two separate sibling classes that each express one of the possiblities

[kryptt]

Here is a long workshop on all the ways to find the different counts:

https://github.com/cohomolo-gy/Isomorphic-Reasoning

We probably don't need this since parametricity is virtually non-existent in C#