Do not require type specification for constructors when the type is known

Do not require type specification for constructors when the type is known.

Imagine this case:

Dictionary<string, List<int>> d = new Dictionary<string, List<int>>();

becomes:

Dictionary<string, List<int>> d = new();

Obviously, constructor arguments and object initialization would be allowed.

This might be a simple optimization given the above example, but there are longer type specifications out there.

But when applied to this:

XmlReader.Create(reader, new XmlReaderSettings{ IgnoreWhitespace = true });

it would become this:

XmlReader.Create(reader, new{ IgnoreWhitespace = true });

which is a lot more readable. In cases like this, the type is not really important, its properties are.

[MadsTorgersen]

This is attractive as a counterpart to deconstruction, and we are considering it for a future version of C#.

[neofuji]

I think it is useful for array initialization.

public int[] indices = new[256];