Highlights:

• Representing data better in code (tuples, object destructuring, pattern matching, record types, array slices)
• Metaprogramming (virtual extension methods, default interface implementations, enhanced generic constraints, mixins/traits, delegation)
• Immutable values (readonly var x ~ val x ~ let x)
• Asynchronous enumeration and streams
• Code contract language integrations
• Structural typing (think implicit interfaces in Go)
• Explicit lambda capture handling (pass by value or reference semantics explicitly)
• Solve null reference problem (Non-nullable references, Option type)