fix BaseType annotation check (#8318)

Author: okhat

dspy/adapters/types/base_type.py

@@ -1,5 +1,6 @@
 import json
 import re
+import inspect
 from typing import Any, Union, get_args, get_origin
 
 import json_repair
@@ -41,9 +42,18 @@ def extract_custom_type_from_annotation(cls, annotation):
         This is used to extract all custom types from the annotation of a field, while the annotation can
         have arbitrary level of nesting. For example, we detect `Tool` is in `list[dict[str, Tool]]`.
         """
-        # Direct match
-        if isinstance(annotation, type) and issubclass(annotation, cls):
-            return [annotation]
+        # Direct match. Some typing constructs (like `typing.Any`, `TypeAlias`,
+        # or weird internals) may pass `isinstance(..., type)` but are not
+        # valid classes for `issubclass`. We defensively guard against this by
+        # using `inspect.isclass` and wrapping the call in a try/except block.
+        try:
+            if inspect.isclass(annotation) and issubclass(annotation, cls):
+                return [annotation]
+        except TypeError:
+            # `issubclass` can raise `TypeError` if the argument is not actually
+            # a class (even if `inspect.isclass` thought otherwise). In these
+            # cases we just ignore the annotation.
+            return []
 
         origin = get_origin(annotation)
         if origin is None: