During template application memo can be used to store results
of a computation in the session. The memo will be automatically
cleared on an event that invalidates the caches.
TypecheckingService has become too overloaded with responsibilities, and
so Strategy class is introduced to extract strategies to.
Cache holder can also be non-tracking, which comes in handy when
implementing purely caching typechecking, not anticipating any change.
As closures typesystem depends on collections due to sequence type,
so collections typesystem depends on closures due to function type.
E.g. consider typechecking of SequenceCreator.
LogicalItemValueExpression is to play the same role as valueOf(logical)
within an instance of EvaluationSubject.
LogicalItemExpression is to represent the logical variable itself.
Introduce SessionData, allow to keep arbitrary data with the session.
Extend RulesListTable with support for invalidation based on rule unique tags.
Introduce UpdatesRecorder to keep track of invalidated nodes.
Extend ApplyTemplatesStep with invalidate logic for typechecking.
Simplify design, drop unnecessary fields, minor refactorings.
Rules that are used only as auxiliary resolvers don't have an associated
origin node, even though they are produced from a specific location.
To enable tracking of correct origin to report errors to one can use
origin(no origin){} to override the default behaviour.
A reusable Config app component to be responsible for all level of configurations: default/system/user/ui.
Swith to Config interface instead of map<string,Object> for options.
Add an UI option to control whether trace is enabled.
In some situations it is unreasonable to fail on missing templates,
it's better to produce a working but perhaps incomplete program
than not to produce anything.
basetag() returns name of ConstraintRule without node id.
Check on whether Rule is principal are now done through basetag(), it's sufficient.
Add part of future analysis: CallerTableBuilder.
Step subclasses are meant to be immutable and stateless.
The state is now encapsulated in Effect subclasses, which can be combined.
Correspondingly, schedule now produces streams of effects.
Fedor Isakov