Fix typing of params ids callable form

The previous typing had an object passed to the user, which they can't
do anything with without asserting, which is inconvenient. Change it to
Any instead.

Note that what comes *back* to pytest (the return value) should be an
`object`, because we want to handle arbitrary objects without assuming
anything about them.

src/_pytest/fixtures.py

@@ -976,7 +976,7 @@ class FixtureDef(Generic[_FixtureValue]):
         ids: Optional[
             Union[
                 Tuple[Union[None, str, float, int, bool], ...],
-                Callable[[object], Optional[object]],
+                Callable[[Any], Optional[object]],
             ]
         ] = None,
     ) -> None:
@@ -1128,13 +1128,13 @@ def _ensure_immutable_ids(
     ids: Optional[
         Union[
             Iterable[Union[None, str, float, int, bool]],
-            Callable[[object], Optional[object]],
+            Callable[[Any], Optional[object]],
         ]
     ],
 ) -> Optional[
     Union[
         Tuple[Union[None, str, float, int, bool], ...],
-        Callable[[object], Optional[object]],
+        Callable[[Any], Optional[object]],
     ]
 ]:
     if ids is None:
@@ -1180,7 +1180,7 @@ class FixtureFunctionMarker:
     ids = attr.ib(
         type=Union[
             Tuple[Union[None, str, float, int, bool], ...],
-            Callable[[object], Optional[object]],
+            Callable[[Any], Optional[object]],
         ],
         default=None,
         converter=_ensure_immutable_ids,
@@ -1223,7 +1223,7 @@ def fixture(
     ids: Optional[
         Union[
             Iterable[Union[None, str, float, int, bool]],
-            Callable[[object], Optional[object]],
+            Callable[[Any], Optional[object]],
         ]
     ] = ...,
     name: Optional[str] = ...
@@ -1241,7 +1241,7 @@ def fixture(  # noqa: F811
     ids: Optional[
         Union[
             Iterable[Union[None, str, float, int, bool]],
-            Callable[[object], Optional[object]],
+            Callable[[Any], Optional[object]],
         ]
     ] = ...,
     name: Optional[str] = None
@@ -1258,7 +1258,7 @@ def fixture(  # noqa: F811
     ids: Optional[
         Union[
             Iterable[Union[None, str, float, int, bool]],
-            Callable[[object], Optional[object]],
+            Callable[[Any], Optional[object]],
         ]
     ] = None,
     name: Optional[str] = None

src/_pytest/mark/structures.py

@@ -433,7 +433,7 @@ if TYPE_CHECKING:
             ids: Optional[
                 Union[
                     Iterable[Union[None, str, float, int, bool]],
-                    Callable[[object], Optional[object]],
+                    Callable[[Any], Optional[object]],
                 ]
             ] = ...,
             scope: Optional[_Scope] = ...

src/_pytest/python.py

@@ -11,6 +11,7 @@ from collections import Counter
 from collections import defaultdict
 from collections.abc import Sequence
 from functools import partial
+from typing import Any
 from typing import Callable
 from typing import Dict
 from typing import Generator
@@ -920,7 +921,7 @@ class Metafunc:
         ids: Optional[
             Union[
                 Iterable[Union[None, str, float, int, bool]],
-                Callable[[object], Optional[object]],
+                Callable[[Any], Optional[object]],
             ]
         ] = None,
         scope: "Optional[_Scope]" = None,
@@ -1040,7 +1041,7 @@ class Metafunc:
         ids: Optional[
             Union[
                 Iterable[Union[None, str, float, int, bool]],
-                Callable[[object], Optional[object]],
+                Callable[[Any], Optional[object]],
             ]
         ],
         parameters: typing.Sequence[ParameterSet],
@@ -1226,7 +1227,7 @@ def _idval(
     val: object,
     argname: str,
     idx: int,
-    idfn: Optional[Callable[[object], Optional[object]]],
+    idfn: Optional[Callable[[Any], Optional[object]]],
     nodeid: Optional[str],
     config: Optional[Config],
 ) -> str:
@@ -1266,7 +1267,7 @@ def _idvalset(
     idx: int,
     parameterset: ParameterSet,
     argnames: Iterable[str],
-    idfn: Optional[Callable[[object], Optional[object]]],
+    idfn: Optional[Callable[[Any], Optional[object]]],
     ids: Optional[List[Union[None, str]]],
     nodeid: Optional[str],
     config: Optional[Config],
@@ -1287,7 +1288,7 @@ def _idvalset(
 def idmaker(
     argnames: Iterable[str],
     parametersets: Iterable[ParameterSet],
-    idfn: Optional[Callable[[object], Optional[object]]] = None,
+    idfn: Optional[Callable[[Any], Optional[object]]] = None,
     ids: Optional[List[Union[None, str]]] = None,
     config: Optional[Config] = None,
     nodeid: Optional[str] = None,

testing/typing_checks.py

@@ -10,3 +10,15 @@ import pytest
 @pytest.mark.xfail(raises=RuntimeError)
 def check_mark_xfail_raises() -> None:
     pass
+
+
+# Issue #7494.
+@pytest.fixture(params=[(0, 0), (1, 1)], ids=lambda x: str(x[0]))
+def check_fixture_ids_callable() -> None:
+    pass
+
+
+# Issue #7494.
+@pytest.mark.parametrize("func", [str, int], ids=lambda x: str(x.__name__))
+def check_parametrize_ids_callable(func) -> None:
+    pass