C#: Extract default parameter values.

[michaelnebel]

It turns out that there is yet another way, one can define a parameter default value by using the attribute (DefaultParameterValue) to instruct the compiler, how the default value should be constructed using an implicit conversion operator.

The following is valid C# code:

public struct MyStruct
{
    public static implicit operator MyStruct(string s) => new MyStruct();
}

public class MyClass
{
    public void M([Optional, DefaultParameterValue("mystring")] MyStruct arg) => throw null;
}

The compiler checks that there exists a way to construct (in this case an implicit conversion operator) a value of type MyStruct from a string.
Intuitively, the definition of M is equivalent to (which is not legal C# code).

public void M(MyStruct arg = "mystring") => throw null;

In this PR we try to emulate this behaviour.

[hvitved]

Looks great to me 🎉

[hvitved]

Did you run DCA already?

[michaelnebel]

Did you run DCA already?

Not yet - but I will do so :-)

[michaelnebel]

DCA looks good!