You must now use 'eval' to get the body of a concept

core/builtin_concepts.py

@@ -44,8 +44,10 @@ class BuiltinConcepts(Enum):
     CONCEPT_EVAL_ERROR = "concept evaluation error"  # cannot evaluate a property or metadata of a concept
     ENUMERATION = "enum"  # represents a list or a set
     LIST = "list"  # represents a list
-    CANNOT_RESOLVE_VALUE_ERROR = "value cannot be resolved"  # don't know how to find concept value
     CONCEPT_ALREADY_IN_SET = "concept already in set"
+    EVALUATOR_PRE_PROCESS = "evaluator pre process"  # used modify / tweak behaviour of evaluators
+    CONCEPT_EVAL_REQUESTED = "concept eval requested"
+    REDUCE_REQUESTED = "reduce requested"  # remove meaningless error when possible
 
     NODE = "node"
     GENERIC_NODE = "generic node"
@@ -68,7 +70,6 @@ BuiltinErrors = [str(e) for e in {
     BuiltinConcepts.INVALID_RETURN_VALUE,
     BuiltinConcepts.CONCEPT_ALREADY_DEFINED,
     BuiltinConcepts.CONCEPT_EVAL_ERROR,
-    BuiltinConcepts.CANNOT_RESOLVE_VALUE_ERROR,
     BuiltinConcepts.CONCEPT_ALREADY_IN_SET,
 }]
 
@@ -267,6 +268,15 @@ class AfterEvaluationConcept(Concept):
         super().__init__(BuiltinConcepts.AFTER_EVALUATION, True, True, BuiltinConcepts.AFTER_EVALUATION)
 
 
+class ConceptEvalRequested(Concept):
+    def __init__(self):
+        super().__init__(BuiltinConcepts.CONCEPT_EVAL_REQUESTED, True, True, BuiltinConcepts.CONCEPT_EVAL_REQUESTED)
+
+
+class ReduceRequested(Concept):
+    def __init__(self):
+        super().__init__(BuiltinConcepts.REDUCE_REQUESTED, True, True, BuiltinConcepts.REDUCE_REQUESTED)
+
 class ConceptEvalError(Concept):
     def __init__(self, error=None, concept=None, property_name=None):
         super().__init__(BuiltinConcepts.CONCEPT_EVAL_ERROR,