[lacampbell]

Base classes already have to carry their runtime type with them anyway. As do nodes of an algebraic data type. You may well be right that the compiler might not be "sufficiently smart" to see this very limited use of dynamic and realise no special reflection magic is actually required. But considering dynamic is only used to actually pull out the runtime type in the example code, and not to call arbitrary methods on it that may or not be there, I assumed - maybe wrongly - that the runtime hit would be the same as the branching that occurs in Ocaml or Haskell or F# when it comes across a "match" statement.

But to answer your question - yes, entirely based on gut reaction and what a compiler would ideally be able to do given the code posted. So very probably wrong.