IsParameterRef trigger scope check split into ScopeHasParameterRef
RuleApply does nothing
Oops: Need to RuleDelete when GetField found its tag
Rule: updateRuleTriggers
UnionFind.unmaintainedRefMapLookup -> OpaqueRefs.refMapUnmaintainedLookup
*Broken*: No AppliedPiResult
*broken*: Does not compile