All deprecation warnings have been converted to errors. This includes
the warning for multiple cfgs on one item. We'll leave that as an error
for some period of time to ensure that all uses are updated before the
behavior changes from "or" to "and".
Stop read+write expressions from expanding into two occurences
in the AST. Add a bool to indicate whether an operand in output
position if read+write or not.
Fixes#14936
