I've been assuming that SOF would not contain support for declaring
the types of variables.  Inlined code thus requires a type check to be
sure you're executing the right code.  If it can be shown that a
particular slot has a value created with a particular type then never
changed, then the type check can be elided.

There's nothing preventing a compiler from doing strict type checking,
but it will have to add the type check code to generated classes.