REF: simplify DTA.__init__ (#47574)

Author: jbrockmendel

pandas/core/arrays/datetimes.py

@@ -256,7 +256,7 @@ def _scalar_type(self) -> type[Timestamp]:
     _freq = None
 
     def __init__(
-        self, values, dtype=DT64NS_DTYPE, freq=lib.no_default, copy: bool = False
+        self, values, dtype=None, freq=lib.no_default, copy: bool = False
     ) -> None:
         values = extract_array(values, extract_numpy=True)
         if isinstance(values, IntegerArray):
@@ -276,22 +276,19 @@ def __init__(
                 freq = to_offset(freq)
                 freq, _ = dtl.validate_inferred_freq(freq, values.freq, False)
 
-            # validation
-            dtz = getattr(dtype, "tz", None)
-            if dtz and values.tz is None:
-                dtype = DatetimeTZDtype(tz=dtype.tz)
-            elif dtz and values.tz:
-                if not timezones.tz_compare(dtz, values.tz):
-                    msg = (
-                        "Timezone of the array and 'dtype' do not match. "
-                        f"'{dtz}' != '{values.tz}'"
+            if dtype is not None:
+                dtype = pandas_dtype(dtype)
+                if not is_dtype_equal(dtype, values.dtype):
+                    raise TypeError(
+                        f"dtype={dtype} does not match data dtype {values.dtype}"
                     )
-                    raise TypeError(msg)
-            elif values.tz:
-                dtype = values.dtype
 
+            dtype = values.dtype
             values = values._ndarray
 
+        elif dtype is None:
+            dtype = DT64NS_DTYPE
+
         if not isinstance(values, np.ndarray):
             raise ValueError(
                 f"Unexpected type '{type(values).__name__}'. 'values' must be a "

pandas/tests/arrays/datetimes/test_constructors.py

@@ -77,9 +77,16 @@ def test_mismatched_timezone_raises(self):
             dtype=DatetimeTZDtype(tz="US/Central"),
         )
         dtype = DatetimeTZDtype(tz="US/Eastern")
-        with pytest.raises(TypeError, match="Timezone of the array"):
+        msg = r"dtype=datetime64\[ns.*\] does not match data dtype datetime64\[ns.*\]"
+        with pytest.raises(TypeError, match=msg):
             DatetimeArray(arr, dtype=dtype)
 
+        # also with mismatched tzawareness
+        with pytest.raises(TypeError, match=msg):
+            DatetimeArray(arr, dtype=np.dtype("M8[ns]"))
+        with pytest.raises(TypeError, match=msg):
+            DatetimeArray(arr.tz_localize(None), dtype=arr.dtype)
+
     def test_non_array_raises(self):
         with pytest.raises(ValueError, match="list"):
             DatetimeArray([1, 2, 3])