Fix crash on ParamSpec with Any callable (#777)

docs/changelog.md

@@ -3,7 +3,7 @@
 ## Unreleased
 
 - Fix various issues with Python 3.13 and 3.14 support (#773)
-- Improve `ParamSpec` support (#772)
+- Improve `ParamSpec` support (#772, #777)
 - Fix handling of stub functions with positional-only parameters with
   defaults (#769)
 - Recognize exhaustive pattern matching (#766)

pyanalyze/signature.py

@@ -1756,6 +1756,11 @@ def substitute_typevars(self, typevars: TypeVarMap) -> "Signature":
                     elif isinstance(new_val, AnyValue):
                         new_param = SigParameter(param.name, ParameterKind.ELLIPSIS)
                         params.append((param.name, new_param))
+                    elif isinstance(new_val, CallValue):
+                        new_param = SigParameter(
+                            param.name, ParameterKind.PARAM_SPEC, annotation=new_val
+                        )
+                        params.append((param.name, new_param))
                     else:
                         assert isinstance(new_val, CallableValue), new_val
                         assert isinstance(new_val.signature, Signature), new_val

pyanalyze/test_annotations.py

@@ -1849,6 +1849,45 @@ def capybara() -> None:
             assert_type(apply(sample, 1), str)
             apply(sample, "x")  # E: incompatible_call
 
+    @assert_passes()
+    def test_apply_bound_method(self):
+        from typing import Callable, TypeVar
+
+        from typing_extensions import ParamSpec, assert_type
+
+        P = ParamSpec("P")
+        T = TypeVar("T")
+
+        def apply(func: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T:
+            return func(*args, **kwargs)
+
+        class X:
+            def sample(self, x: int) -> str:
+                return str(x)
+
+        def capybara(x: X) -> None:
+            assert_type(apply(x.sample, 1), str)
+            apply(x.sample, "x")  # E: incompatible_call
+
+    @assert_passes()
+    def test_apply_any(self):
+        from typing import Any, Callable, TypeVar
+
+        from typing_extensions import ParamSpec, assert_type
+
+        P = ParamSpec("P")
+        T = TypeVar("T")
+
+        def apply(func: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T:
+            return func(*args, **kwargs)
+
+        def capybara(x, args, kwargs) -> None:
+            assert_type(apply(x, 1), Any)
+            assert_type(apply(x.foo, 1), Any)
+            assert_type(apply(x), Any)
+            assert_type(apply(x, y=3), Any)
+            assert_type(apply(x, *args, **kwargs), Any)
+
     @assert_passes()
     def test_param_spec_errors(self):
         from typing import Callable, TypeVar