CLN: remove never-hit branch from maybe_infer_to_datetimelike (#40109)

Author: jbrockmendel

pandas/_libs/lib.pyx

@@ -1562,7 +1562,7 @@ def infer_datetimelike_array(arr: ndarray[object]) -> str:
                 seen_tz_aware = True
 
             if seen_tz_naive and seen_tz_aware:
-                return 'mixed'
+                return "mixed"
         elif util.is_datetime64_object(v):
             # np.datetime64
             seen_datetime = True

pandas/core/dtypes/cast.py

@@ -698,7 +698,7 @@ def maybe_promote(dtype: np.dtype, fill_value=np.nan):
     return dtype, fill_value
 
 
-def _ensure_dtype_type(value, dtype: DtypeObj):
+def _ensure_dtype_type(value, dtype: np.dtype):
     """
     Ensure that the given value is an instance of the given dtype.
 
@@ -708,21 +708,17 @@ def _ensure_dtype_type(value, dtype: DtypeObj):
     Parameters
     ----------
     value : object
-    dtype : np.dtype or ExtensionDtype
+    dtype : np.dtype
 
     Returns
     -------
     object
     """
     # Start with exceptions in which we do _not_ cast to numpy types
-    if is_extension_array_dtype(dtype):
-        return value
-    elif dtype == np.object_:
-        return value
-    elif isna(value):
-        # e.g. keep np.nan rather than try to cast to np.float32(np.nan)
+    if dtype == np.object_:
         return value
 
+    # Note: before we get here we have already excluded isna(value)
     return dtype.type(value)
 
 
@@ -1139,7 +1135,7 @@ def astype_nansafe(
     if isinstance(dtype, ExtensionDtype):
         return dtype.construct_array_type()._from_sequence(arr, dtype=dtype, copy=copy)
 
-    elif not isinstance(dtype, np.dtype):
+    elif not isinstance(dtype, np.dtype):  # pragma: no cover
         raise ValueError("dtype must be np.dtype or ExtensionDtype")
 
     if arr.dtype.kind in ["m", "M"] and (
@@ -1389,9 +1385,7 @@ def maybe_castable(dtype: np.dtype) -> bool:
     return dtype.name not in POSSIBLY_CAST_DTYPES
 
 
-def maybe_infer_to_datetimelike(
-    value: Union[np.ndarray, List], convert_dates: bool = False
-):
+def maybe_infer_to_datetimelike(value: Union[np.ndarray, List]):
     """
     we might have a array (or single object) that is datetime like,
     and no dtype is passed don't change the value unless we find a
@@ -1403,13 +1397,10 @@ def maybe_infer_to_datetimelike(
     Parameters
     ----------
     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 not isinstance(value, (np.ndarray, list)):
-        raise TypeError(type(value))
+        raise TypeError(type(value))  # pragma: no cover
 
     v = np.array(value, copy=False)
 
@@ -1466,9 +1457,7 @@ def try_timedelta(v: np.ndarray) -> np.ndarray:
 
     inferred_type = lib.infer_datetimelike_array(ensure_object(v))
 
-    if inferred_type == "date" and convert_dates:
-        value = try_datetime(v)
-    elif inferred_type == "datetime":
+    if inferred_type == "datetime":
         value = try_datetime(v)
     elif inferred_type == "timedelta":
         value = try_timedelta(v)

pandas/core/tools/datetimes.py

@@ -248,13 +248,13 @@ def _convert_and_box_cache(
     return _box_as_indexlike(result, utc=None, name=name)
 
 
-def _return_parsed_timezone_results(result, timezones, tz, name):
+def _return_parsed_timezone_results(result: np.ndarray, timezones, tz, name) -> Index:
     """
     Return results from array_strptime if a %z or %Z directive was passed.
 
     Parameters
     ----------
-    result : ndarray
+    result : ndarray[int64]
         int64 date representations of the dates
     timezones : ndarray
         pytz timezone objects
@@ -287,7 +287,7 @@ def _convert_listlike_datetimes(
     infer_datetime_format: Optional[bool] = None,
     dayfirst: Optional[bool] = None,
     yearfirst: Optional[bool] = None,
-    exact: Optional[bool] = None,
+    exact: bool = True,
 ):
     """
     Helper function for to_datetime. Performs the conversions of 1D listlike
@@ -311,7 +311,7 @@ def _convert_listlike_datetimes(
         dayfirst parsing behavior from to_datetime
     yearfirst : boolean
         yearfirst parsing behavior from to_datetime
-    exact : boolean
+    exact : bool, default True
         exact format matching behavior from to_datetime
 
     Returns