REF: privatize maybe_cast_to_extension_array (pandas-dev#53061)

Author: jbrockmendel

pandas/core/arrays/base.py

@@ -38,7 +38,7 @@
     validate_insert_loc,
 )
 
-from pandas.core.dtypes.cast import maybe_cast_to_extension_array
+from pandas.core.dtypes.cast import maybe_cast_pointwise_result
 from pandas.core.dtypes.common import (
     is_list_like,
     is_scalar,
@@ -1957,7 +1957,7 @@ def _maybe_convert(arr):
                     # https://github.com/pandas-dev/pandas/issues/22850
                     # We catch all regular exceptions here, and fall back
                     # to an ndarray.
-                    res = maybe_cast_to_extension_array(type(self), arr)
+                    res = maybe_cast_pointwise_result(arr, self.dtype, same_dtype=False)
                     if not isinstance(res, type(self)):
                         # exception raised in _from_sequence; ensure we have ndarray
                         res = np.asarray(arr)

pandas/core/dtypes/cast.py

@@ -67,7 +67,6 @@
     PeriodDtype,
 )
 from pandas.core.dtypes.generic import (
-    ABCExtensionArray,
     ABCIndex,
     ABCSeries,
 )
@@ -463,17 +462,17 @@ def maybe_cast_pointwise_result(
 
             cls = dtype.construct_array_type()
             if same_dtype:
-                result = maybe_cast_to_extension_array(cls, result, dtype=dtype)
+                result = _maybe_cast_to_extension_array(cls, result, dtype=dtype)
             else:
-                result = maybe_cast_to_extension_array(cls, result)
+                result = _maybe_cast_to_extension_array(cls, result)
 
     elif (numeric_only and dtype.kind in "iufcb") or not numeric_only:
         result = maybe_downcast_to_dtype(result, dtype)
 
     return result
 
 
-def maybe_cast_to_extension_array(
+def _maybe_cast_to_extension_array(
     cls: type[ExtensionArray], obj: ArrayLike, dtype: ExtensionDtype | None = None
 ) -> ArrayLike:
     """
@@ -492,10 +491,6 @@ def maybe_cast_to_extension_array(
     """
     from pandas.core.arrays.string_ import BaseStringArray
 
-    assert isinstance(cls, type), f"must pass a type: {cls}"
-    assertion_msg = f"must pass a subclass of ExtensionArray: {cls}"
-    assert issubclass(cls, ABCExtensionArray), assertion_msg
-
     # Everything can be converted to StringArrays, but we may not want to convert
     if issubclass(cls, BaseStringArray) and lib.infer_dtype(obj) != "string":
         return obj