class check

toy-impl/inheritance.py

@@ -0,0 +1,25 @@
+from helper import *
+from type_def import *
+import copy
+
+def class_fixup(c: ClassType):
+    if c.checking:
+        raise CustomError(f'Circular inheritance detected')
+    if c.checked:
+        return
+    c.checking = True
+    for p in c.parents:
+        class_fixup(p)
+        for m in p.methods:
+            if m in c.methods:
+                old = p.methods[m]
+                new = c.methods[m]
+                if old[0] != new[0] or old[1] != new[1]:
+                    # actually, we should check for equality *modulo variable renaming*
+                    raise CustomError(f'incorrect method signature for {m} in {c.name}')
+            else:
+                c.methods[m] = p.methods[m]
+    c.checking = False
+    c.checked = True
+
+

toy-impl/type_def.py

@@ -73,13 +73,15 @@ class TypeVariable(Type):
 class ClassType(Type):
     name: str
     parents: list['ClassType']
-    methods: dict[str, tuple[list[Type], Type, set[str]]]
-    fields: dict[str, Type]
+    checking: bool
+    checked: bool
 
     def __init__(self, name: str):
         super().__init__()
         self.name    = name
         self.parents = []
+        self.checking = False
+        self.checked = False
 
     def __str__(self):
         return self.name