Fix mutable optional attribute if using shared annotation type

dltype/_lib/_core.py

@@ -5,6 +5,7 @@
 import inspect
 import itertools
 import warnings
+from copy import copy
 from functools import lru_cache, wraps
 from types import EllipsisType
 from typing import (
@@ -124,6 +125,7 @@ def from_hint(  # noqa: PLR0911
             msg = f"Invalid base type=<{tensor_type}> in DLType hint, expected a subtype of {_dtypes.SUPPORTED_TENSOR_TYPES}"
             raise TypeError(msg)
 
+        dltype_hint = copy(dltype_hint) if optional else dltype_hint
         dltype_hint.optional = optional
         return (cls(tensor_type_hint=tensor_type, dltype_annotation=dltype_hint),)
 

dltype/tests/dltype_test.py

@@ -1711,3 +1711,24 @@ def tuple_function(
             ) -> Self:
                 """A function that takes a tensor and returns a tensor."""
                 return self
+
+
+SomeTensorT: TypeAlias = Annotated[torch.Tensor, dltype.FloatTensor["1 2 3"]]
+
+
+def test_aliased_optional() -> None:
+
+    @dltype.dltyped()
+    def func(non_optional_tensor: SomeTensorT, optional_tensor: SomeTensorT | None = None) -> None:
+        pass
+
+    func(torch.zeros((1, 2, 3)))
+
+    func(torch.zeros((1, 2, 3)), None)
+
+    func(torch.zeros((1, 2, 3)), torch.zeros((1, 2, 3)))
+
+    func(torch.zeros((1, 2, 3)))
+
+    with pytest.raises(dltype.DLTypeUnsupportedTensorTypeError):
+        func(None, torch.zeros((1, 2, 3)))  # pyright: ignore[reportArgumentType]