diff --git a/examples/01_simple_type_checking/04_complex_types.midas b/examples/01_simple_type_checking/04_complex_types.midas
index b561cef..adc76b3 100644
--- a/examples/01_simple_type_checking/04_complex_types.midas
+++ b/examples/01_simple_type_checking/04_complex_types.midas
@@ -1,8 +1,8 @@
 type Meter = float
 
 extend Meter {
-    def __add__: fn(Meter) -> Meter
-    def __sub__: fn(Meter) -> Meter
+    def __add__: fn(Meter, /) -> Meter
+    def __sub__: fn(Meter, /) -> Meter
 }
 
 type Coordinate = object
diff --git a/midas/checker/python.py b/midas/checker/python.py
index cf25593..88ecde0 100644
--- a/midas/checker/python.py
+++ b/midas/checker/python.py
@@ -78,6 +78,12 @@ class PythonTyper(
         self.judgements.append((expr, type))
         return type
 
+    def resolve_type_expr(self, expr: p.MidasType) -> Type:
+        return expr.accept(self)
+
+    def process_stmt(self, stmt: p.Stmt) -> None:
+        stmt.accept(self)
+
     def process_block(self, block: list[p.Stmt], env: Environment) -> bool:
         """Evaluate a sequence of statements
 
@@ -93,7 +99,7 @@ class PythonTyper(
         returned: bool = False
         for i, stmt in enumerate(block):
             try:
-                stmt.accept(self)
+                self.process_stmt(stmt)
             except ReturnException:
                 returned = True
                 if i < len(block) - 1:
@@ -111,7 +117,7 @@ class PythonTyper(
             statements (list[p.Stmt]): the statements to evaluate and check
         """
         for stmt in statements:
-            stmt.accept(self)
+            self.process_stmt(stmt)
 
         self.logger.debug(f"Final environment: {self.env.flat_dict()}")
 
@@ -144,9 +150,9 @@ class PythonTyper(
 
         def eval_arg_type(arg: p.Function.Argument) -> Type:
             if arg.type is not None:
-                return arg.type.accept(self)
+                return self.resolve_type_expr(arg.type)
             if arg.default is not None:
-                return arg.default.accept(self)
+                return self.type_of(arg.default)
             return UnknownType()
 
         pos: int = 0
@@ -186,7 +192,7 @@ class PythonTyper(
 
         returns_hint: Optional[Type] = None
         if stmt.returns is not None:
-            returns_hint = stmt.returns.accept(self)
+            returns_hint = self.resolve_type_expr(stmt.returns)
             # Early define to handle simple fully-typed recursion
             inside_function: Function = Function(
                 pos_args=pos_args,
@@ -232,7 +238,7 @@ class PythonTyper(
 
     def visit_type_assign(self, stmt: p.TypeAssign) -> None:
         # TODO check not yet defined locally
-        type: Type = stmt.type.accept(self)
+        type: Type = self.resolve_type_expr(stmt.type)
         self.env.define(stmt.name, type)
 
     def visit_assign_stmt(self, stmt: p.AssignStmt) -> None:
@@ -287,7 +293,7 @@ class PythonTyper(
             )
 
     def visit_return_stmt(self, stmt: p.ReturnStmt) -> None:
-        type: Type = stmt.value.accept(self) if stmt.value is not None else UnitType()
+        type: Type = self.type_of(stmt.value) if stmt.value is not None else UnitType()
         self.env.return_types.append(type)
         raise ReturnException()
 
@@ -297,7 +303,7 @@ class PythonTyper(
         # if (m := 1 + 1) < 2:
         #     ...
         # print(m)  # <- m is still defined
-        test_type: Type = stmt.test.accept(self)
+        test_type: Type = self.type_of(stmt.test)
 
         # TODO Allow subtypes or any type
         if test_type != self.types.get_type("bool"):
@@ -419,8 +425,8 @@ class PythonTyper(
         return type or UnknownType()
 
     def visit_logical_expr(self, expr: p.LogicalExpr) -> Type:
-        left: Type = expr.left.accept(self)
-        right: Type = expr.right.accept(self)
+        left: Type = self.type_of(expr.left)
+        right: Type = self.type_of(expr.right)
 
         if self.is_subtype(left, right):
             return right
@@ -434,10 +440,10 @@ class PythonTyper(
         return UnknownType()
 
     def visit_cast_expr(self, expr: p.CastExpr) -> Type:
-        return expr.type.accept(self)
+        return self.resolve_type_expr(expr.type)
 
     def visit_ternary_expr(self, expr: p.TernaryExpr) -> Type:
-        test_type: Type = expr.test.accept(self)
+        test_type: Type = self.type_of(expr.test)
 
         # TODO Allow subtypes or any type
         if test_type != self.types.get_type("bool"):
@@ -445,8 +451,8 @@ class PythonTyper(
                 expr.test.location, f"If test must be a boolean, got {test_type}"
             )
 
-        true_type: Type = expr.if_true.accept(self)
-        false_type: Type = expr.if_false.accept(self)
+        true_type: Type = self.type_of(expr.if_true)
+        false_type: Type = self.type_of(expr.if_false)
         if self.is_subtype(true_type, false_type):
             return false_type
         if self.is_subtype(false_type, true_type):
@@ -484,7 +490,7 @@ class PythonTyper(
             return UnknownType()
 
         if node.param is not None:
-            param: Type = node.param.accept(self)
+            param: Type = self.resolve_type_expr(node.param)
             return self.types.apply_generic(base, [param])
         return base