REF: tighter types in maybe_infer_to_datetimelike (#40086)

Author: jbrockmendel

pandas/core/arrays/categorical.py

@@ -398,6 +398,10 @@ def __init__(
         elif not isinstance(values, (ABCIndex, ABCSeries, ExtensionArray)):
             # sanitize_array coerces np.nan to a string under certain versions
             # of numpy
+            if not isinstance(values, (np.ndarray, list)):
+                # convert e.g. range, tuple to allow for stronger typing
+                #  of maybe_infer_to_datetimelike
+                values = list(values)
             values = maybe_infer_to_datetimelike(values)
             if isinstance(values, np.ndarray):
                 values = sanitize_to_nanoseconds(values)

pandas/core/construction.py

@@ -670,7 +670,7 @@ def _try_cast(
         else:
             subarr = maybe_cast_to_datetime(arr, dtype)
 
-        if not isinstance(subarr, (ABCExtensionArray, ABCIndex)):
+        if not isinstance(subarr, ABCExtensionArray):
             subarr = construct_1d_ndarray_preserving_na(subarr, dtype, copy=copy)
     except OutOfBoundsDatetime:
         # in case of out of bound datetime64 -> always raise

pandas/core/dtypes/cast.py

@@ -96,7 +96,6 @@
 from pandas.core.dtypes.generic import (
     ABCDataFrame,
     ABCExtensionArray,
-    ABCIndex,
     ABCSeries,
 )
 from pandas.core.dtypes.inference import is_list_like
@@ -1389,7 +1388,7 @@ def maybe_castable(dtype: np.dtype) -> bool:
 
 
 def maybe_infer_to_datetimelike(
-    value: Union[ArrayLike, Scalar], convert_dates: bool = False
+    value: Union[np.ndarray, List], convert_dates: bool = False
 ):
     """
     we might have a array (or single object) that is datetime like,
@@ -1401,21 +1400,16 @@ def maybe_infer_to_datetimelike(
 
     Parameters
     ----------
-    value : np.array / Series / Index / list-like
+    value : np.ndarray or list
     convert_dates : bool, default False
        if True try really hard to convert dates (such as datetime.date), other
        leave inferred dtype 'date' alone
 
     """
-    if isinstance(value, (ABCIndex, ABCExtensionArray)):
-        if not is_object_dtype(value.dtype):
-            raise ValueError("array-like value must be object-dtype")
+    if not isinstance(value, (np.ndarray, list)):
+        raise TypeError(type(value))
 
-    v = value
-
-    if not is_list_like(v):
-        v = [v]
-    v = np.array(v, copy=False)
+    v = np.array(value, copy=False)
 
     # we only care about object dtypes
     if not is_object_dtype(v.dtype):
@@ -1616,7 +1610,7 @@ def maybe_cast_to_datetime(
         elif value.dtype == object:
             value = maybe_infer_to_datetimelike(value)
 
-    else:
+    elif not isinstance(value, ABCExtensionArray):
         # only do this if we have an array and the dtype of the array is not
         # setup already we are not an integer/object, so don't bother with this
         # conversion