Why isn't a new () general constraint satisfied by a class with optional parameters in the constructor?

Question

The following code cannot be compiled, creating the error "The widget must not be an abstract type with an open constructor without parameters." I would think that the compiler has all the necessary information. This is mistake? Supervision? Or is there some kind of scenario when this is not valid?

public class Factory<T> where T : new()
{
    public T Build()
    {
        return new T();
    }
}

public class Widget
{
    public Widget(string name = "foo")
    {
        Name = name;
    }

    public string Name { get; set; }
}

public class Program
{
    public static void Main()
    {
        var widget = new Widget(); // this is valid
        var factory = new Factory<Widget>(); // compiler error
    }
}

Answer 1

Although this should work logically, unfortunately this does not happen. The CLR still sees your constructor as a parameter-based constructor.

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public Widget(([Optional, DefaultParameterValue("foo")] string name) { // ...

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Edit:

:

, # CLR

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public Widget(
          int id = 0, 
          string name = "foo", 
          float width=1.0f, 
          float height=1.0f, 
          float depth=1.0f
       ) { // ... 

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