var firstName = "David";
var lastName = "Pine";
var dateOfBirth = new Date(1984, 7, 7);

// C# 7.0, required "explicit names"
var person = (firstName: firstName, lastName: lastName, dateOfBirth: dateOfBirth);
person.firstName;   // "David"
person.lastName;    // "Pine"
person.dateOfBirth  // 7/7/1984

// C# 7.1, allows "inferred names"
person = (firstName, lastName, dateOfBirth);
person.firstName;   // "David"
person.lastName;    // "Pine"
person.dateOfBirth  // 7/7/1984

const int x = default;
return default;

In C# 7.1, the language extends the valid signatures of an entrypoint to allow these async overloads of the Main method to be valid.

public static void Main();
public static int Main();
public static void Main(string[] args);
public static int Main(string[] args);
public static Task Main();
public static Task<int> Main();
public static Task Main(string[] args);
public static Task<int> Main(string[] args);