Improve SA1131 to also consider methods as constants

[bjornhellander]

The following code triggers SA1131 (Use readable conditions) :

// Totally contrived example code :-) Only here to illustrate the current behaviour.
class TestClass
{
    private readonly System.Action myAction;

    public TestClass(bool stuff)
    {
        myAction = stuff ? DoSomething : DoSomethingElse;
    }

    public bool MyCondition => myAction == DoSomething; // SA1131 here!

    private void DoSomething()
    {
    }

    private void DoSomethingElse()
    {
    }
}

The code fix changes the condition like this:
public bool MyCondition => DoSomething == myAction;

DoSomething is in effect a constant in that condition, so I think that SA1131 should not be triggered.
Unusual case, but might be worth considering if the change is easy?

Tested with 1.2.0-beta.507.

[sharwell]

Are you sure that example produces SA1131?

[bjornhellander]

But what the... No, it doesn't. But it did. I think. :-)
Let me try to de-simplify this again. I'll be back.

[bjornhellander]

Ah, it triggers if the field is static readonly. The example needs some changes, but this triggers for example:

class TestClass
{
    private static readonly System.Action myAction;

    static TestClass()
    {
        var someMoreElaborateCondition = true;
        myAction = someMoreElaborateCondition ? DoSomething : DoSomethingElse;
    }

    public bool MyCondition => myAction == DoSomething; // SA1131 here!

    private static void DoSomething()
    {
    }

    private static void DoSomethingElse()
    {
    }
}

[sharwell]

It seems fine to make this change.