From 5804098e153da39ac4c1180e3c43a5545a1564e7 Mon Sep 17 00:00:00 2001
From: Simon Hawkins <simonjayhawkins@gmail.com>
Date: Tue, 2 Nov 2021 20:22:34 +0000
Subject: [PATCH 1/3] overload infer_dtype_from_array

---
 pandas/core/algorithms.py  |  6 +-----
 pandas/core/dtypes/cast.py | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/pandas/core/algorithms.py b/pandas/core/algorithms.py
index c1b587ce3a6b2..6708096d4f528 100644
--- a/pandas/core/algorithms.py
+++ b/pandas/core/algorithms.py
@@ -1723,11 +1723,7 @@ def safe_sort(
     if not isinstance(values, (np.ndarray, ABCExtensionArray)):
         # don't convert to string types
         dtype, _ = infer_dtype_from_array(values)
-        # error: Argument "dtype" to "asarray" has incompatible type "Union[dtype[Any],
-        # ExtensionDtype]"; expected "Union[dtype[Any], None, type, _SupportsDType, str,
-        # Union[Tuple[Any, int], Tuple[Any, Union[int, Sequence[int]]], List[Any],
-        # _DTypeDict, Tuple[Any, Any]]]"
-        values = np.asarray(values, dtype=dtype)  # type: ignore[arg-type]
+        values = np.asarray(values, dtype=dtype)
 
     sorter = None
 
diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index c0ac9098ec7fc..6b4fe68d65a8b 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -14,6 +14,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    Literal,
     Sized,
     TypeVar,
     cast,
@@ -795,6 +796,25 @@ def dict_compat(d: dict[Scalar, Scalar]) -> dict[Scalar, Scalar]:
     return {maybe_box_datetimelike(key): value for key, value in d.items()}
 
 
+@overload
+def infer_dtype_from_array(
+    arr,
+) -> tuple[np.dtype, ArrayLike]:
+    ...
+
+
+@overload
+def infer_dtype_from_array(
+    arr, pandas_dtype: Literal[False] = ...
+) -> tuple[np.dtype, ArrayLike]:
+    ...
+
+
+@overload
+def infer_dtype_from_array(arr, pandas_dtype: bool = ...) -> tuple[DtypeObj, ArrayLike]:
+    ...
+
+
 def infer_dtype_from_array(
     arr, pandas_dtype: bool = False
 ) -> tuple[DtypeObj, ArrayLike]:

From 2caa77dc7e3f17bca3893e6c0673332fe6431241 Mon Sep 17 00:00:00 2001
From: Simon Hawkins <simonjayhawkins@gmail.com>
Date: Tue, 2 Nov 2021 20:41:22 +0000
Subject: [PATCH 2/3] is_complex_dtype in _ensure_data

---
 pandas/core/algorithms.py | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/pandas/core/algorithms.py b/pandas/core/algorithms.py
index 6708096d4f528..2876921824c27 100644
--- a/pandas/core/algorithms.py
+++ b/pandas/core/algorithms.py
@@ -165,10 +165,8 @@ def _ensure_data(values: ArrayLike) -> np.ndarray:
         return np.asarray(values)
 
     elif is_complex_dtype(values.dtype):
-        # Incompatible return value type (got "Tuple[Union[Any, ExtensionArray,
-        # ndarray[Any, Any]], Union[Any, ExtensionDtype]]", expected
-        # "Tuple[ndarray[Any, Any], Union[dtype[Any], ExtensionDtype]]")
-        return values  # type: ignore[return-value]
+        assert isinstance(values, np.ndarray)  # for mypy
+        return values
 
     # datetimelike
     elif needs_i8_conversion(values.dtype):

From 4f9a72dc803b48d0c493bac335d650423ab27d47 Mon Sep 17 00:00:00 2001
From: Simon Hawkins <simonjayhawkins@gmail.com>
Date: Tue, 2 Nov 2021 21:05:31 +0000
Subject: [PATCH 3/3] update _ensure_data docstring

---
 pandas/core/algorithms.py | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/pandas/core/algorithms.py b/pandas/core/algorithms.py
index 2876921824c27..011f9c2a680cb 100644
--- a/pandas/core/algorithms.py
+++ b/pandas/core/algorithms.py
@@ -112,16 +112,19 @@
 # --------------- #
 def _ensure_data(values: ArrayLike) -> np.ndarray:
     """
-    routine to ensure that our data is of the correct
-    input dtype for lower-level routines
+    Ensure values is of the correct input dtype for lower-level routines.
 
     This will coerce:
     - ints -> int64
     - uint -> uint64
-    - bool -> uint64 (TODO this should be uint8)
+    - bool -> uint8
     - datetimelike -> i8
     - datetime64tz -> i8 (in local tz)
     - categorical -> codes
+    - categorical[bool] without nulls -> uint8
+    - categorical[bool] with nulls -> ValueError: cannot convert float NaN to integer
+    - boolean without nulls -> uint8
+    - boolean with nulls -> object
 
     Parameters
     ----------