[BUG] Validate dtype when Int64Index, UInt64Index, or Float64Index are cons…

doc/source/whatsnew/v1.0.0.rst

@@ -336,6 +336,7 @@ Numeric
 - Bug in :class:`DataFrame` logical operations (`&`, `|`, `^`) not matching :class:`Series` behavior by filling NA values (:issue:`28741`)
 - Bug in :meth:`DataFrame.interpolate` where specifying axis by name references variable before it is assigned (:issue:`29142`)
 - Improved error message when using `frac` > 1 and `replace` = False (:issue:`27451`)
+- Bug in :class:`NumericIndex` resulted in it being possible to instantiate an :class:`Int64Index`, :class:`UInt64Index`, or :class:`Float64Index` with an invalid dtype (e.g. datetime-like) (:issue:`29539`)
 -
 
 Conversion

pandas/core/indexes/base.py

@@ -380,7 +380,7 @@ def __new__(
                             pass
 
                         # Return an actual float index.
-                        return Float64Index(data, copy=copy, dtype=dtype, name=name)
+                        return Float64Index(data, copy=copy, name=name)
 
                     elif inferred == "string":
                         pass

pandas/core/indexes/numeric.py

@@ -15,6 +15,8 @@
     is_float_dtype,
     is_integer_dtype,
     is_scalar,
+    is_signed_integer_dtype,
+    is_unsigned_integer_dtype,
     needs_i8_conversion,
     pandas_dtype,
 )
@@ -45,7 +47,7 @@ class NumericIndex(Index):
     _is_numeric_dtype = True
 
     def __new__(cls, data=None, dtype=None, copy=False, name=None, fastpath=None):
-
+        cls._validate_dtype(cls, dtype)
         if fastpath is not None:
             warnings.warn(
                 "The 'fastpath' keyword is deprecated, and will be "
@@ -72,6 +74,25 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None, fastpath=None):
             name = data.name
         return cls._simple_new(subarr, name=name)
 
+    def _validate_dtype(cls, dtype):
+        if dtype is None:
+            return
+        if cls._typ == "int64index" and not is_signed_integer_dtype(dtype):
+            raise ValueError(
+                "Incorrect `dtype` passed: expected signed integer, received {}".format(
+                    dtype
+                )
+            )
+        elif cls._typ == "uint64index" and not is_unsigned_integer_dtype(dtype):
+            raise ValueError(
+                "Incorrect `dtype` passed: expected unsigned integer"
+                ", received {}".format(dtype)
+            )
+        elif cls._typ == "float64index" and not is_float_dtype(dtype):
+            raise ValueError(
+                "Incorrect `dtype` passed: expected float, received {}".format(dtype)
+            )
+
     @Appender(_index_shared_docs["_maybe_cast_slice_bound"])
     def _maybe_cast_slice_bound(self, label, side, kind):
         assert kind in ["ix", "loc", "getitem", None]

pandas/tests/indexes/test_numeric.py

@@ -167,6 +167,22 @@ def test_constructor(self):
         result = Index(np.array([np.nan]))
         assert pd.isna(result.values).all()
 
+    @pytest.mark.parametrize(
+        "index, dtype",
+        [
+            (pd.Int64Index, "float64"),
+            (pd.UInt64Index, "categorical"),
+            (pd.Float64Index, "datetime64"),
+        ],
+    )
+    def test_invalid_dtype(self, index, dtype):
+        # GH 29539
+        with pytest.raises(
+            ValueError,
+            match=r"Incorrect `dtype` passed: expected .*, received {}".format(dtype),
+        ):
+            index([1, 2, 3], dtype=dtype)
+
     def test_constructor_invalid(self):
 
         # invalid

pandas/tests/series/indexing/test_numeric.py

@@ -86,8 +86,7 @@ def test_get():
                 1764.0,
                 1849.0,
                 1936.0,
-            ],
-            dtype="object",
+            ]
         ),
     )