Language Support: Anonymous Derivations

[prasannavl]

Anonymous derivation for classes and interfaces, providing the illusion of direct instantiation of interfaces, base classes, etc.

public interface IRandom {
 void SayHello();
 string GetString();
}

Its is impossible to use the existing new operator without colliding with current semantics. But introducing another keyword has its own problems, and compatibilities issues. Instead, simply use the new keyword, but as the constraint form, new() except that it takes an argument of syntax typeName { InitializationExpression } where the expression similar to the class initialization syntax, except that, all functions, are described as expressions.

new(IRandom { 
  SayHello = () => {
     Console.WriteLine("Hello!");
  },
  GetString = Func<string> => {
  return "Hello";
},
})

The Funcs aren't really funcs. They get translated into real methods by Roslyn. This is only used for the expression definition.

The above is a compile-time factor. This can also be extended to be done at run-time with a new overload, that takes a type as parameter, there-by providing the language with direct interface instantiation-like semantics.

[HaloFour]

This would be a dupe of #13 and #1728.

[gafter]

Closing as a dup of #13.