diff --git a/pandas/_libs/tslibs/conversion.pyx b/pandas/_libs/tslibs/conversion.pyx
index cb13cde7a4bed..1b20ffbe52493 100644
--- a/pandas/_libs/tslibs/conversion.pyx
+++ b/pandas/_libs/tslibs/conversion.pyx
@@ -61,7 +61,6 @@ from pandas._libs.tslibs.nattype cimport (
     c_nat_strings as nat_strings,
 )
 from pandas._libs.tslibs.parsing cimport parse_datetime_string
-from pandas._libs.tslibs.timestamps cimport _Timestamp
 from pandas._libs.tslibs.timezones cimport (
     get_utcoffset,
     is_utc,
@@ -761,7 +760,7 @@ cdef int64_t parse_pydatetime(
             _ts.ensure_reso(NPY_FR_ns)
             result = _ts.value
     else:
-        if isinstance(val, _Timestamp):
+        if isinstance(val, ABCTimestamp):
             result = val.as_unit("ns")._value
         else:
             result = pydatetime_to_dt64(val, dts)
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index fd89d0e795ecc..3e1554e8b79b3 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -22,7 +22,7 @@ from numpy cimport (
 
 cnp.import_array()
 
-from cpython.datetime cimport (  # alias bc `tzinfo` is a kwarg below
+from cpython.datetime cimport (  # alias tzinfo_type bc `tzinfo` is a kwarg below
     PyDate_Check,
     PyDateTime_Check,
     PyDelta_Check,
diff --git a/pandas/_libs/tslibs/util.pxd b/pandas/_libs/tslibs/util.pxd
index 4e55bc1c48fd0..243c65a6e516e 100644
--- a/pandas/_libs/tslibs/util.pxd
+++ b/pandas/_libs/tslibs/util.pxd
@@ -10,6 +10,7 @@ cdef extern from "Python.h":
     bint PyComplex_Check(object obj) nogil
     bint PyObject_TypeCheck(object obj, PyTypeObject* type) nogil
 
+    # TODO(cython3): cimport this, xref GH#49670
     # Note that following functions can potentially raise an exception,
     # thus they cannot be declared 'nogil'. Also PyUnicode_AsUTF8AndSize() can
     # potentially allocate memory inside in unlikely case of when underlying
diff --git a/pandas/core/computation/align.py b/pandas/core/computation/align.py
index fff605eb7cf59..a8ca08c58c261 100644
--- a/pandas/core/computation/align.py
+++ b/pandas/core/computation/align.py
@@ -133,9 +133,8 @@ def _align_core(terms):
                         w, category=PerformanceWarning, stacklevel=find_stack_level()
                     )
 
-                f = partial(ti.reindex, reindexer, axis=axis, copy=False)
-
-                terms[i].update(f())
+                obj = ti.reindex(reindexer, axis=axis, copy=False)
+                terms[i].update(obj)
 
         terms[i].update(terms[i].value.values)
 
diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index 3929775283f6a..2d45158cf2a9f 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -50,7 +50,6 @@
     ensure_str,
     is_bool,
     is_complex,
-    is_extension_array_dtype,
     is_float,
     is_integer,
     is_object_dtype,
@@ -903,7 +902,8 @@ def infer_dtype_from_array(
     if not is_list_like(arr):
         raise TypeError("'arr' must be list-like")
 
-    if pandas_dtype and is_extension_array_dtype(arr):
+    arr_dtype = getattr(arr, "dtype", None)
+    if pandas_dtype and isinstance(arr_dtype, ExtensionDtype):
         return arr.dtype, arr
 
     elif isinstance(arr, ABCSeries):
diff --git a/pandas/core/dtypes/missing.py b/pandas/core/dtypes/missing.py
index 2fb8d3563b792..4e854ff3cf91a 100644
--- a/pandas/core/dtypes/missing.py
+++ b/pandas/core/dtypes/missing.py
@@ -26,7 +26,6 @@
     TD64NS_DTYPE,
     ensure_object,
     is_dtype_equal,
-    is_extension_array_dtype,
     is_scalar,
     is_string_or_object_np_dtype,
 )
@@ -56,6 +55,7 @@
         npt,
     )
 
+    from pandas import Series
     from pandas.core.indexes.base import Index
 
 
@@ -642,11 +642,11 @@ def na_value_for_dtype(dtype: DtypeObj, compat: bool = True):
     return np.nan
 
 
-def remove_na_arraylike(arr):
+def remove_na_arraylike(arr: Series | Index | np.ndarray):
     """
     Return array-like containing only true/non-NaN values, possibly empty.
     """
-    if is_extension_array_dtype(arr):
+    if isinstance(arr.dtype, ExtensionDtype):
         return arr[notna(arr)]
     else:
         return arr[notna(np.asarray(arr))]
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 9cbb652b33b46..f3de296841510 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -590,6 +590,7 @@ def _get_cleaned_column_resolvers(self) -> dict[Hashable, Series]:
             clean_column_name(k): v for k, v in self.items() if not isinstance(k, int)
         }
 
+    @final
     @property
     def _info_axis(self) -> Index:
         return getattr(self, self._info_axis_name)
@@ -969,6 +970,7 @@ def squeeze(self, axis: Axis | None = None):
     # ----------------------------------------------------------------------
     # Rename
 
+    @final
     def _rename(
         self,
         mapper: Renamer | None = None,
@@ -3476,6 +3478,7 @@ def _wrap(x, alt_format_):
             render_kwargs=render_kwargs_,
         )
 
+    @final
     def _to_latex_via_styler(
         self,
         buf=None,
@@ -4293,6 +4296,7 @@ def _check_setitem_copy(self, t: str = "setting", force: bool_t = False):
         if value == "warn":
             warnings.warn(t, SettingWithCopyWarning, stacklevel=find_stack_level())
 
+    @final
     def __delitem__(self, key) -> None:
         """
         Delete item
@@ -6069,6 +6073,7 @@ def __finalize__(self, other, method: str | None = None, **kwargs) -> Self:
 
         return self
 
+    @final
     def __getattr__(self, name: str):
         """
         After regular attribute access, try looking up the name
@@ -6085,6 +6090,7 @@ def __getattr__(self, name: str):
             return self[name]
         return object.__getattribute__(self, name)
 
+    @final
     def __setattr__(self, name: str, value) -> None:
         """
         After regular attribute access, try setting the name
@@ -6255,6 +6261,7 @@ def dtypes(self):
         data = self._mgr.get_dtypes()
         return self._constructor_sliced(data, index=self._info_axis, dtype=np.object_)
 
+    @final
     def astype(
         self, dtype, copy: bool_t | None = None, errors: IgnoreRaise = "raise"
     ) -> Self:
@@ -7128,6 +7135,7 @@ def ffill(
     ) -> Self | None:
         ...
 
+    @final
     @doc(klass=_shared_doc_kwargs["klass"])
     def ffill(
         self,
@@ -7149,6 +7157,7 @@ def ffill(
             method="ffill", axis=axis, inplace=inplace, limit=limit, downcast=downcast
         )
 
+    @final
     @doc(klass=_shared_doc_kwargs["klass"])
     def pad(
         self,
@@ -7211,6 +7220,7 @@ def bfill(
     ) -> Self | None:
         ...
 
+    @final
     @doc(klass=_shared_doc_kwargs["klass"])
     def bfill(
         self,
@@ -7232,6 +7242,7 @@ def bfill(
             method="bfill", axis=axis, inplace=inplace, limit=limit, downcast=downcast
         )
 
+    @final
     @doc(klass=_shared_doc_kwargs["klass"])
     def backfill(
         self,
@@ -7501,6 +7512,7 @@ def replace(
         else:
             return result.__finalize__(self, method="replace")
 
+    @final
     def interpolate(
         self,
         method: Literal[
@@ -8185,6 +8197,7 @@ def _clip_with_one_bound(self, threshold, method, axis, inplace):
         # GH 40420
         return self.where(subset, threshold, axis=axis, inplace=inplace)
 
+    @final
     def clip(
         self,
         lower=None,
@@ -9996,6 +10009,7 @@ def where(
     ) -> Self | None:
         ...
 
+    @final
     @doc(
         klass=_shared_doc_kwargs["klass"],
         cond="True",
@@ -10188,6 +10202,7 @@ def mask(
     ) -> Self | None:
         ...
 
+    @final
     @doc(
         where,
         klass=_shared_doc_kwargs["klass"],
@@ -10368,6 +10383,7 @@ def shift(
         result = self.set_axis(new_ax, axis=axis)
         return result.__finalize__(self, method="shift")
 
+    @final
     def truncate(
         self,
         before=None,
@@ -11693,46 +11709,56 @@ def _inplace_method(self, other, op) -> Self:
         )
         return self
 
+    @final
     def __iadd__(self, other) -> Self:
         # error: Unsupported left operand type for + ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__add__)  # type: ignore[operator]
 
+    @final
     def __isub__(self, other) -> Self:
         # error: Unsupported left operand type for - ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__sub__)  # type: ignore[operator]
 
+    @final
     def __imul__(self, other) -> Self:
         # error: Unsupported left operand type for * ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__mul__)  # type: ignore[operator]
 
+    @final
     def __itruediv__(self, other) -> Self:
         # error: Unsupported left operand type for / ("Type[NDFrame]")
         return self._inplace_method(
             other, type(self).__truediv__  # type: ignore[operator]
         )
 
+    @final
     def __ifloordiv__(self, other) -> Self:
         # error: Unsupported left operand type for // ("Type[NDFrame]")
         return self._inplace_method(
             other, type(self).__floordiv__  # type: ignore[operator]
         )
 
+    @final
     def __imod__(self, other) -> Self:
         # error: Unsupported left operand type for % ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__mod__)  # type: ignore[operator]
 
+    @final
     def __ipow__(self, other) -> Self:
         # error: Unsupported left operand type for ** ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__pow__)  # type: ignore[operator]
 
+    @final
     def __iand__(self, other) -> Self:
         # error: Unsupported left operand type for & ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__and__)  # type: ignore[operator]
 
+    @final
     def __ior__(self, other) -> Self:
         # error: Unsupported left operand type for | ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__or__)  # type: ignore[operator]
 
+    @final
     def __ixor__(self, other) -> Self:
         # error: Unsupported left operand type for ^ ("Type[NDFrame]")
         return self._inplace_method(other, type(self).__xor__)  # type: ignore[operator]
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index fe24f9b7c4d7f..694f2201d9f34 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -922,18 +922,20 @@ def __array_ufunc__(self, ufunc: np.ufunc, method: str_t, *inputs, **kwargs):
 
         return self.__array_wrap__(result)
 
+    @final
     def __array_wrap__(self, result, context=None):
         """
         Gets called after a ufunc and other functions e.g. np.split.
         """
         result = lib.item_from_zerodim(result)
         if (
-            (not isinstance(result, Index) and is_bool_dtype(result))
+            (not isinstance(result, Index) and is_bool_dtype(result.dtype))
             or lib.is_scalar(result)
             or np.ndim(result) > 1
         ):
             # exclude Index to avoid warning from is_bool_dtype deprecation;
             #  in the Index case it doesn't matter which path we go down.
+            # reached in plotting tests with e.g. np.nonzero(index)
             return result
 
         return Index(result, name=self.name)
diff --git a/pandas/core/indexes/category.py b/pandas/core/indexes/category.py
index 4854a919fb272..d2ef607635abb 100644
--- a/pandas/core/indexes/category.py
+++ b/pandas/core/indexes/category.py
@@ -17,6 +17,7 @@
 )
 
 from pandas.core.dtypes.common import is_scalar
+from pandas.core.dtypes.concat import concat_compat
 from pandas.core.dtypes.dtypes import CategoricalDtype
 from pandas.core.dtypes.missing import (
     is_valid_na_for_dtype,
@@ -478,7 +479,6 @@ def _concat(self, to_concat: list[Index], name: Hashable) -> Index:
             )
         except TypeError:
             # not all to_concat elements are among our categories (or NA)
-            from pandas.core.dtypes.concat import concat_compat
 
             res = concat_compat([x._values for x in to_concat])
             return Index(res, name=name)
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index ca01b1fd5fe6f..13c87a9d06b66 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -113,6 +113,7 @@
 
 
 def _get_next_label(label):
+    # see test_slice_locs_with_ints_and_floats_succeeds
     dtype = getattr(label, "dtype", type(label))
     if isinstance(label, (Timestamp, Timedelta)):
         dtype = "datetime64[ns]"
@@ -129,6 +130,7 @@ def _get_next_label(label):
 
 
 def _get_prev_label(label):
+    # see test_slice_locs_with_ints_and_floats_succeeds
     dtype = getattr(label, "dtype", type(label))
     if isinstance(label, (Timestamp, Timedelta)):
         dtype = "datetime64[ns]"
diff --git a/pandas/core/reshape/melt.py b/pandas/core/reshape/melt.py
index df9112faa2a47..8e61754002cdb 100644
--- a/pandas/core/reshape/melt.py
+++ b/pandas/core/reshape/melt.py
@@ -10,10 +10,7 @@
 
 from pandas.util._decorators import Appender
 
-from pandas.core.dtypes.common import (
-    is_extension_array_dtype,
-    is_list_like,
-)
+from pandas.core.dtypes.common import is_list_like
 from pandas.core.dtypes.concat import concat_compat
 from pandas.core.dtypes.missing import notna
 
@@ -126,7 +123,8 @@ def melt(
     mdata: dict[Hashable, AnyArrayLike] = {}
     for col in id_vars:
         id_data = frame.pop(col)
-        if is_extension_array_dtype(id_data):
+        if not isinstance(id_data.dtype, np.dtype):
+            # i.e. ExtensionDtype
             if K > 0:
                 mdata[col] = concat([id_data] * K, ignore_index=True)
             else:
diff --git a/pandas/core/reshape/pivot.py b/pandas/core/reshape/pivot.py
index 0f775f959c4ce..e5cd2f51e6165 100644
--- a/pandas/core/reshape/pivot.py
+++ b/pandas/core/reshape/pivot.py
@@ -18,12 +18,12 @@
 
 from pandas.core.dtypes.cast import maybe_downcast_to_dtype
 from pandas.core.dtypes.common import (
-    is_extension_array_dtype,
     is_integer_dtype,
     is_list_like,
     is_nested_list_like,
     is_scalar,
 )
+from pandas.core.dtypes.dtypes import ExtensionDtype
 from pandas.core.dtypes.generic import (
     ABCDataFrame,
     ABCSeries,
@@ -326,7 +326,7 @@ def _add_margins(
     row_names = result.index.names
     # check the result column and leave floats
     for dtype in set(result.dtypes):
-        if is_extension_array_dtype(dtype):
+        if isinstance(dtype, ExtensionDtype):
             # Can hold NA already
             continue
 
diff --git a/pandas/core/reshape/reshape.py b/pandas/core/reshape/reshape.py
index e14a0e681b02c..65fd9137313f1 100644
--- a/pandas/core/reshape/reshape.py
+++ b/pandas/core/reshape/reshape.py
@@ -21,7 +21,6 @@
 from pandas.core.dtypes.common import (
     ensure_platform_int,
     is_1d_only_ea_dtype,
-    is_extension_array_dtype,
     is_integer,
     needs_i8_conversion,
 )
@@ -47,6 +46,7 @@
 
 if TYPE_CHECKING:
     from pandas._typing import (
+        ArrayLike,
         Level,
         npt,
     )
@@ -591,13 +591,14 @@ def factorize(index):
             verify_integrity=False,
         )
 
+    new_values: ArrayLike
     if not frame.empty and frame._is_homogeneous_type:
         # For homogeneous EAs, frame._values will coerce to object. So
         # we concatenate instead.
         dtypes = list(frame.dtypes._values)
         dtype = dtypes[0]
 
-        if is_extension_array_dtype(dtype):
+        if isinstance(dtype, ExtensionDtype):
             arr = dtype.construct_array_type()
             new_values = arr._concat_same_type(
                 [col._values for _, col in frame.items()]
@@ -753,7 +754,7 @@ def _convert_level_number(level_num: int, columns: Index):
         else:
             subset = this.iloc[:, loc]
             dtype = find_common_type(subset.dtypes.tolist())
-            if is_extension_array_dtype(dtype):
+            if isinstance(dtype, ExtensionDtype):
                 # TODO(EA2D): won't need special case, can go through .values
                 #  paths below (might change to ._values)
                 value_slice = dtype.construct_array_type()._concat_same_type(
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 43ebdc2f9dff0..96971736f113b 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -5606,9 +5606,6 @@ def _binop(self, other: Series, func, level=None, fill_value=None) -> Series:
         -------
         Series
         """
-        if not isinstance(other, Series):
-            raise AssertionError("Other operand must be Series")
-
         this = self
 
         if not self.index.equals(other.index):
@@ -5674,7 +5671,7 @@ def _flex_method(self, other, op, *, level=None, fill_value=None, axis: Axis = 0
                 raise ValueError("Lengths must be equal")
             other = self._constructor(other, self.index, copy=False)
             result = self._binop(other, op, level=level, fill_value=fill_value)
-            result.name = res_name
+            result._name = res_name
             return result
         else:
             if fill_value is not None:
diff --git a/pandas/io/json/_table_schema.py b/pandas/io/json/_table_schema.py
index 7decab539da34..97680923554d5 100644
--- a/pandas/io/json/_table_schema.py
+++ b/pandas/io/json/_table_schema.py
@@ -316,7 +316,7 @@ def build_table_schema(
     return schema
 
 
-def parse_table_schema(json, precise_float):
+def parse_table_schema(json, precise_float: bool) -> DataFrame:
     """
     Builds a DataFrame from a given schema
 
diff --git a/pandas/plotting/_matplotlib/core.py b/pandas/plotting/_matplotlib/core.py
index d1e8f92ffc36b..f11d663f39cea 100644
--- a/pandas/plotting/_matplotlib/core.py
+++ b/pandas/plotting/_matplotlib/core.py
@@ -22,7 +22,6 @@
 
 from pandas.core.dtypes.common import (
     is_any_real_numeric_dtype,
-    is_extension_array_dtype,
     is_float,
     is_float_dtype,
     is_hashable,
@@ -33,7 +32,10 @@
     is_number,
     is_numeric_dtype,
 )
-from pandas.core.dtypes.dtypes import CategoricalDtype
+from pandas.core.dtypes.dtypes import (
+    CategoricalDtype,
+    ExtensionDtype,
+)
 from pandas.core.dtypes.generic import (
     ABCDataFrame,
     ABCIndex,
@@ -567,9 +569,9 @@ def _convert_to_ndarray(self, data):
             return data
 
         # GH32073: cast to float if values contain nulled integers
-        if (
-            is_integer_dtype(data.dtype) or is_float_dtype(data.dtype)
-        ) and is_extension_array_dtype(data.dtype):
+        if (is_integer_dtype(data.dtype) or is_float_dtype(data.dtype)) and isinstance(
+            data.dtype, ExtensionDtype
+        ):
             return data.to_numpy(dtype="float", na_value=np.nan)
 
         # GH25587: cast ExtensionArray of pandas (IntegerArray, etc.) to
diff --git a/pandas/tests/strings/test_cat.py b/pandas/tests/strings/test_cat.py
index ff2898107a9e4..a6303610b2037 100644
--- a/pandas/tests/strings/test_cat.py
+++ b/pandas/tests/strings/test_cat.py
@@ -13,13 +13,6 @@
 )
 
 
-def assert_series_or_index_equal(left, right):
-    if isinstance(left, Series):
-        tm.assert_series_equal(left, right)
-    else:  # Index
-        tm.assert_index_equal(left, right)
-
-
 @pytest.mark.parametrize("other", [None, Series, Index])
 def test_str_cat_name(index_or_series, other):
     # GH 21053
@@ -57,11 +50,11 @@ def test_str_cat(index_or_series):
 
     # Series/Index with array
     result = s.str.cat(t, na_rep="-")
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with list
     result = s.str.cat(list(t), na_rep="-")
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # errors for incorrect lengths
     rgx = r"If `others` contains arrays or lists \(or other list-likes.*"
@@ -100,16 +93,16 @@ def test_str_cat_categorical(index_or_series, dtype_caller, dtype_target, sep):
 
     # Series/Index with unaligned Index -> t.values
     result = s.str.cat(t.values, sep=sep)
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with Series having matching Index
     t = Series(t.values, index=s)
     result = s.str.cat(t, sep=sep)
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with Series.values
     result = s.str.cat(t.values, sep=sep)
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with Series having different Index
     t = Series(t.values, index=t.values)
@@ -117,7 +110,7 @@ def test_str_cat_categorical(index_or_series, dtype_caller, dtype_target, sep):
     expected = expected if box == Index else Series(expected, index=expected.str[:1])
 
     result = s.str.cat(t, sep=sep)
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
 
 @pytest.mark.parametrize(
@@ -155,37 +148,37 @@ def test_str_cat_mixed_inputs(index_or_series):
 
     # Series/Index with DataFrame
     result = s.str.cat(d)
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with two-dimensional ndarray
     result = s.str.cat(d.values)
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with list of Series
     result = s.str.cat([t, s])
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with mixed list of Series/array
     result = s.str.cat([t, s.values])
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with list of Series; different indexes
     t.index = ["b", "c", "d", "a"]
     expected = box(["aDa", "bAb", "cBc", "dCd"])
     expected = expected if box == Index else Series(expected.values, index=s.values)
     result = s.str.cat([t, s])
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with mixed list; different index
     result = s.str.cat([t, s.values])
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # Series/Index with DataFrame; different indexes
     d.index = ["b", "c", "d", "a"]
     expected = box(["aDd", "bAa", "cBb", "dCc"])
     expected = expected if box == Index else Series(expected.values, index=s.values)
     result = s.str.cat(d)
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # errors for incorrect lengths
     rgx = r"If `others` contains arrays or lists \(or other list-likes.*"
@@ -261,7 +254,7 @@ def test_str_cat_align_indexed(index_or_series, join):
         expected = Index(expected)
 
     result = s.str.cat(t, join=join, na_rep="-")
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
 
 @pytest.mark.parametrize("join", ["left", "outer", "inner", "right"])
@@ -332,7 +325,7 @@ def test_str_cat_all_na(index_or_series, index_or_series2):
     else:  # box == Index
         expected = Index([np.nan] * 4, dtype=object)
     result = s.str.cat(t, join="left")
-    assert_series_or_index_equal(result, expected)
+    tm.assert_equal(result, expected)
 
     # all-NA caller (only for Series)
     if other == Series:
diff --git a/pandas/tseries/holiday.py b/pandas/tseries/holiday.py
index 34812aa491cd3..70190b16767cf 100644
--- a/pandas/tseries/holiday.py
+++ b/pandas/tseries/holiday.py
@@ -149,6 +149,10 @@ class Holiday:
     for observance.
     """
 
+    start_date: Timestamp | None
+    end_date: Timestamp | None
+    days_of_week: tuple[int, ...] | None
+
     def __init__(
         self,
         name: str,
@@ -242,7 +246,9 @@ def __repr__(self) -> str:
         repr = f"Holiday: {self.name} ({info})"
         return repr
 
-    def dates(self, start_date, end_date, return_name: bool = False):
+    def dates(
+        self, start_date, end_date, return_name: bool = False
+    ) -> Series | DatetimeIndex:
         """
         Calculate holidays observed between start date and end date
 
@@ -253,6 +259,11 @@ def dates(self, start_date, end_date, return_name: bool = False):
         return_name : bool, optional, default=False
             If True, return a series that has dates and holiday names.
             False will only return dates.
+
+        Returns
+        -------
+        Series or DatetimeIndex
+            Series if return_name is True
         """
         start_date = Timestamp(start_date)
         end_date = Timestamp(end_date)
@@ -262,16 +273,21 @@ def dates(self, start_date, end_date, return_name: bool = False):
 
         if self.year is not None:
             dt = Timestamp(datetime(self.year, self.month, self.day))
+            dti = DatetimeIndex([dt])
             if return_name:
-                return Series(self.name, index=[dt])
+                return Series(self.name, index=dti)
             else:
-                return [dt]
+                return dti
 
         dates = self._reference_dates(start_date, end_date)
         holiday_dates = self._apply_rule(dates)
         if self.days_of_week is not None:
             holiday_dates = holiday_dates[
-                np.in1d(holiday_dates.dayofweek, self.days_of_week)
+                np.in1d(
+                    # error: "DatetimeIndex" has no attribute "dayofweek"
+                    holiday_dates.dayofweek,  # type: ignore[attr-defined]
+                    self.days_of_week,
+                )
             ]
 
         if self.start_date is not None:
@@ -289,7 +305,9 @@ def dates(self, start_date, end_date, return_name: bool = False):
             return Series(self.name, index=holiday_dates)
         return holiday_dates
 
-    def _reference_dates(self, start_date, end_date):
+    def _reference_dates(
+        self, start_date: Timestamp, end_date: Timestamp
+    ) -> DatetimeIndex:
         """
         Get reference dates for the holiday.
 
@@ -322,7 +340,7 @@ def _reference_dates(self, start_date, end_date):
 
         return dates
 
-    def _apply_rule(self, dates):
+    def _apply_rule(self, dates: DatetimeIndex) -> DatetimeIndex:
         """
         Apply the given offset/observance to a DatetimeIndex of dates.
 
@@ -459,9 +477,16 @@ def holidays(self, start=None, end=None, return_name: bool = False):
                 rule.dates(start, end, return_name=True) for rule in self.rules
             ]
             if pre_holidays:
-                holidays = concat(pre_holidays)
+                # error: Argument 1 to "concat" has incompatible type
+                # "List[Union[Series, DatetimeIndex]]"; expected
+                # "Union[Iterable[DataFrame], Mapping[<nothing>, DataFrame]]"
+                holidays = concat(pre_holidays)  # type: ignore[arg-type]
             else:
-                holidays = Series(index=DatetimeIndex([]), dtype=object)
+                # error: Incompatible types in assignment (expression has type
+                # "Series", variable has type "DataFrame")
+                holidays = Series(
+                    index=DatetimeIndex([]), dtype=object
+                )  # type: ignore[assignment]
 
             self._cache = (start, end, holidays.sort_index())