Type propagation

[dethe]

Types should propagate in a couple of ways:

1. Dropping a typed expression into an any value should change the value to be that type.
2. Dropping an any expression into a typed value should change the any expression to be that type.
   Original types should be stored in a "origType" attribute and restored when the dropped block is removed.

Note that these can cascade through a system if there were several any expressions nested and one becomes typed.
For arrays, if every value in an array is the same type, then returning an item from that array should be that type. This is where it starts to get a bit complicated, because we don't want to prevent putting a string into an array of numbers, for instance.

[dethe]

For arrays, I think a type dropdown on the array constructor should limit all values in the array to the chosen type (especially useful for C / Arduino / Java wrappers) rather than trying to guess from user interactions.