We can now use concept sets in BNF definitions

parsers/BnfParser.py

@@ -127,15 +127,12 @@ class BnfParser(BaseParser):
         except LexerError as e:
             self.add_error(e, False)
 
+        value = self.get_return_value_body(context.sheerka, self.source, tree, tree)
+
         ret = self.sheerka.ret(
             self.name,
             not self.has_error,
-            self.sheerka.new(
-                BuiltinConcepts.PARSER_RESULT,
-                parser=self,
-                source=self.source,
-                body=self.error_sink if self.has_error else tree,
-                try_parsed=tree))
+            value)
 
         return ret
 
@@ -231,15 +228,26 @@ class BnfParser(BaseParser):
 
         if token.type == TokenKind.IDENTIFIER:
             self.next_token()
-            return ConceptExpression(token.value)
-            # concept = self.sheerka.get(str(token.value))
-            # if hasattr(concept, "__iter__") or self.sheerka.isinstance(concept, BuiltinConcepts.UNKNOWN_CONCEPT):
-            #     self.add_error(CannotResolveConceptNode(str(token.value)))
-            #     self.next_token()
-            #     return None
-            # else:
-            #     self.next_token()
-            #     return concept
+
+            concept_name = str(token.value)
+
+            # we are trying to match against a concept which is still under construction !
+            # (for example of recursive bnf definition)
+            if self.context.obj and hasattr(self.context.obj, "name"):
+                if concept_name == str(self.context.obj.name):
+                    return ConceptExpression(concept_name)
+
+            concept = self.context.get_concept(concept_name)
+            if not self.sheerka.is_known(concept):
+                self.add_error(concept)
+                return None
+            elif hasattr(concept, "__iter__"):
+                self.add_error(
+                    self.sheerka.new(BuiltinConcepts.CANNOT_RESOLVE_CONCEPT,
+                                     body=("key", concept_name)))
+                return None
+            else:
+                return concept
 
         ret = StrMatch(core.utils.strip_quotes(token.value))
         self.next_token()