Added concept 'isa' other_concept functionality

parsers/DefaultParser.py

@@ -96,6 +96,12 @@ class DefConceptNode(DefaultParserNode):
         return asts
 
 
+@dataclass()
+class IsaConceptNode(DefaultParserNode):
+    concept: NameNode = NotInitializedNode()
+    set: NameNode = NotInitializedNode()
+
+
 class DefaultParser(BaseParser):
     """
     Parse sheerka specific grammar (like def concept)
@@ -220,7 +226,7 @@ class DefaultParser(BaseParser):
             self.context.log(self.verbose_log, "Keyword DEF found.", self.name)
             return self.parse_def_concept(token)
         else:
-            return self.add_error(CannotHandleErrorNode([], self.text))
+            return self.parse_isa_concept()
 
     def parse_def_concept(self, def_token):
         """
@@ -257,6 +263,35 @@ class DefaultParser(BaseParser):
 
         return concept_found
 
+    def parse_isa_concept(self):
+        concept_name = self.parse_concept_name()
+        if isinstance(concept_name, DefaultParserErrorNode):
+            return concept_name
+
+        keyword = []
+        token = self.get_token()
+        if token.value != Keywords.ISA:
+            return self.add_error(CannotHandleErrorNode([token], ""))
+        keyword.append(token)
+        self.next_token()
+
+        set_name = self.parse_concept_name()
+        return IsaConceptNode(keyword, concept_name, set_name)
+
+    def parse_concept_name(self):
+        tokens = []
+        token = self.get_token()
+
+        while not (token.type == TokenKind.EOF or token.type == TokenKind.KEYWORD):
+            tokens.append(token)
+            self.next_token()
+            token = self.get_token()
+
+        if len(tokens) == 0:
+            return self.add_error(UnexpectedTokenErrorNode([token], "Unexpected token", []))
+        else:
+            return NameNode(tokens)
+
     def regroup_tokens_by_parts(self, keywords_tokens):
 
         def_concept_parts = [Keywords.CONCEPT, Keywords.FROM, Keywords.AS, Keywords.WHERE, Keywords.PRE, Keywords.POST]