Fixed Concatenate raising TypeError in check_callable()

Fixes #338.

docs/features.rst

@@ -24,7 +24,7 @@ The following type checks are not yet supported in Typeguard:
 * Stubs defined with :func:`@overload <typing.overload>` (the implementation is checked
   if instrumented)
 * ``yield_from`` statements in generator functions
-* ``ParamSpec`` is currently ignored
+* ``ParamSpec`` and ``Concatenate`` are currently ignored
 
 Other limitations
 -----------------

docs/versionhistory.rst

@@ -9,6 +9,8 @@ This library adheres to `Semantic Versioning 2.0 <https://semver.org/#semantic-v
   (``SomeType[...]``) being replaced with ``Any[...]`` instead of just ``Any``
 - Fixed instrumentation inadvertently mutating a function's annotations on Python 3.7
   and 3.8
+- Fixed ``Concatenate[...]`` in ``Callable`` parameters causing ``TypeError`` to be
+  raised
 
 **4.0.0rc3** (2023-04-10)
 

src/typeguard/_checkers.py

@@ -158,7 +158,9 @@ def check_callable(
             return
 
         argument_types = args[0]
-        if argument_types is not Ellipsis:
+        if isinstance(argument_types, list) and not any(
+            type(item) is ParamSpec for item in argument_types
+        ):
             # The callable must not have keyword-only arguments without defaults
             unfulfilled_kwonlyargs = [
                 param.name

tests/test_checkers.py

@@ -64,9 +64,9 @@
     from typing_extensions import LiteralString
 
 if sys.version_info >= (3, 10):
-    from typing import TypeGuard
+    from typing import Concatenate, ParamSpec, TypeGuard
 else:
-    from typing_extensions import TypeGuard
+    from typing_extensions import Concatenate, ParamSpec, TypeGuard
 
 if sys.version_info >= (3, 9):
     from typing import Annotated
@@ -78,6 +78,8 @@
 else:
     from typing_extensions import Literal, TypedDict
 
+P = ParamSpec("P")
+
 
 class TestAnyStr:
     @pytest.mark.parametrize(
@@ -257,6 +259,10 @@ def test_builtin(self):
         """
         check_type([].append, Callable[[int], Any])
 
+    def test_concatenate(self):
+        """Test that ``Concatenate`` in the arglist is ignored."""
+        check_type([].append, Callable[Concatenate[object, P], Any])
+
 
 class TestLiteral:
     def test_literal_union(self):