Instead of simple allowed/not option sometimes Unsafe
is useful. 'Unsafe' status may be present when there're
few "bad" rules.
With this level end code may resolve to go with
incrementality without strict guarantees.
Fixes IncrClassHierarchy.modifyClsHierarchyTypeParams test.
Key point is that changes to rules causing their
regeneration must be reflected in program.
There appeared to be cases when it's not true.
It's a case of non-principal rules with origins.
Such rules are called "weak principal" rules.
Matches of weak principal rules are not recorded
in Journal (as is for principal rules), but instead
they become part of their parent MatchChunk.
(In essense, tags of weak principal rules are
recorded in parent chunk).
With this, when a weak principal rule changes,
matches of all principal rules whose computation
depends on them are correctly invalidated.
(Example rules: findHierarchy_Classifier)
Relevant for MPSCR-62.
Now Evidence isn't unique for each Chunk: Occurrence Chunks fully
share evidence and justifications with their activating match.
So, less collections of justifications are created, approx. 2 times less.
Relates to machinery introduced in MPSCR-47.
Previously parent match was maintained in Controller on Java call stack.
Now this stack of parent matches is maintained manually in MatchJournal.
So MatchJournal gains new invariant: parentChunk()
returns correct parent after each logMatch() call.
Several tests fail, also need to maintain this
invariant after logActivation() calls.
Make Occurrence a Justified entity and drop .justifications() from
ConstraintOccurrence.java because justifications are used only internally.
A single justification is now called Evidence (typealias to Int),
so Justified entities are justified by Evidence-s.
StateFrameStack adds no functionality but requires too much processing.
Rename StateFrameStack -> LogicalState.
Rename ProcessingStateImpl -> ConstraintsProcessing.
Simplify occurrence's logical observer.
Introduce transient dependency on controller to LogicalState.
Keep logical state as part of session token, avoid re-initializing
all logical observers.
Make replaying of match journal independent of controller.
It caused a situation when on the very next incremental evaluation session
occurrences carried a stale Controller along with all the state from previous session.
As a result, incorrect logic of program evaluation.
Small changes: rename MatchHistory -> StateAwareJournal; use referential
eq when iterating through chunks; provide only Pos, not Chunk from
current()/currentPos(); fix tests according to all this.
Fedor Isakov