feat: add basic closures

examples/14_closure.peb

@@ -0,0 +1,17 @@
+fun make_counter() {
+    let i = 0
+    fun count() {
+        i += 1
+        return i
+    }
+    return count
+}
+
+let counter = make_counter()
+
+print(counter)
+
+print(counter())
+counter()
+counter()
+print(counter())

main.py

@@ -7,7 +7,7 @@ from src.token import Token
 
 
 def main():
-    path: str = "examples/13_return.peb"
+    path: str = "examples/14_closure.peb"
     source: str = ""
     with open(path, "r") as f:
         source = f.read()

src/core/function.py

@@ -12,14 +12,15 @@ if TYPE_CHECKING:
 
 
 class PebbleFunction(PebbleCallable):
-    def __init__(self, declaration: FunctionStmt):
+    def __init__(self, declaration: FunctionStmt, closure: Environment):
         self.declaration: FunctionStmt = declaration
+        self.closure: Environment = closure
 
     def arity(self) -> int:
         return len(self.declaration.params)
 
     def call(self, interpreter: Interpreter, arguments: list[Any]) -> Any:
-        env: Environment = Environment(interpreter.global_env)
+        env: Environment = Environment(self.closure)
         for i, param in enumerate(self.declaration.params):
             env.define(param.lexeme, arguments[i])
 

src/interpreter/interpreter.py

@@ -146,7 +146,7 @@ class Interpreter(Expr.Visitor[Any], Stmt.Visitor[None]):
         self.evaluate(stmt.expression)
 
     def visit_function_stmt(self, stmt: FunctionStmt) -> None:
-        function: PebbleFunction = PebbleFunction(stmt)
+        function: PebbleFunction = PebbleFunction(stmt, self.env)
         self.env.define(stmt.name.lexeme, function)
 
     def visit_if_stmt(self, stmt: IfStmt) -> None: