Keep unresolvable deferred annotations in inferred signatures on Python 3.14

src/pynguin/analyses/typesystem.py

@@ -35,6 +35,9 @@
 import networkx as nx
 from networkx.drawing.nx_pydot import to_pydot
 
+if sys.version_info >= (3, 14):
+    import annotationlib
+
 import pynguin.configuration as config
 import pynguin.utils.typetracing as tt
 from pynguin.analyses.string_subtypes import infer_regex_from_methods
@@ -2369,7 +2372,15 @@ def infer_signature(
         """
         method_for_signature = get_method_for_signature(method)
         try:
-            method_signature = inspect.signature(method_for_signature)
+            if sys.version_info >= (3, 14):
+                # Deferred annotations (PEP 649) may name types imported only for
+                # type checking, which raises NameError in the default VALUE format.
+                method_signature = inspect.signature(
+                    method_for_signature,
+                    annotation_format=annotationlib.Format.FORWARDREF,
+                )
+            else:
+                method_signature = inspect.signature(method_for_signature)
         except (ValueError, TypeError):
             method_signature = inspect.Signature(
                 parameters=[

tests/analyses/test_typesystem.py

@@ -9,6 +9,7 @@
 import inspect
 import operator
 import re
+import sys
 from typing import Any, ParamSpec, TypeVar, Union
 from unittest import mock
 
@@ -192,6 +193,16 @@ def test_infer_type_info(func, infer_types, expected_parameters, expected_return
     assert result.return_type == expected_return
 
 
+@pytest.mark.skipif(sys.version_info < (3, 14), reason="Annotations are deferred from Python 3.14")
+def test_infer_type_info_annotation_imported_for_type_checking():
+    from tests.fixtures.types.deferred_annotations import length  # noqa: PLC0415
+
+    type_system = TypeSystem()
+    result = type_system.infer_type_info(length, type_inference_provider=HintInference())
+    assert list(result.signature.parameters) == ["obj"]
+    assert result.original_parameters == {"obj": AnyType()}
+
+
 A = TypeVar("A")
 
 

tests/fixtures/types/deferred_annotations.py

@@ -0,0 +1,14 @@
+#  This file is part of Pynguin.
+#
+#  SPDX-FileCopyrightText: 2019–2026 Pynguin Contributors
+#
+#  SPDX-License-Identifier: MIT
+#
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from collections.abc import Sized
+
+
+def length(obj: Sized) -> int:
+    return len(obj)