feat: add basic class instance

examples/basic/17_class.peb

@@ -8,4 +8,6 @@ class Breakfast {
     }
 }
 
-print(Breakfast)
+print(Breakfast)
+let bf = Breakfast()
+print(bf)

src/core/instance.py

@@ -0,0 +1,14 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from src.core.klass import PebbleClass
+
+
+class PebbleInstance:
+    def __init__(self, klass: PebbleClass):
+        self.klass: PebbleClass = klass
+
+    def __str__(self):
+        return f"<instance of {self.klass}>"

src/core/klass.py

@@ -1,6 +1,24 @@
-class PebbleClass:
+from __future__ import annotations
+
+from typing import Any, TYPE_CHECKING
+
+from src.core.callable import PebbleCallable
+from src.core.instance import PebbleInstance
+
+if TYPE_CHECKING:
+    from src.interpreter.interpreter import Interpreter
+
+
+class PebbleClass(PebbleCallable):
     def __init__(self, name: str):
         self.name: str = name
 
     def __str__(self):
         return self.name
+
+    def arity(self) -> int:
+        return 0
+
+    def call(self, interpreter: Interpreter, arguments: list[Any]) -> Any:
+        instance: PebbleInstance = PebbleInstance(self)
+        return instance