3.9.7 option(warn)

If this option is set some constructs which may lead to bug will result in a warning. While there are legitimate uses for them and they are not errors is is worth thinking about it.

• change of options during a procedure call: is this side effect intended?
• use of def: avoids type checking, but useful if a procedure handles several types at once
• ASSUME outside of procedures: while a failed ASSUME aborts the current procedures and return to the top level - what should it do at top level?