TYP: fix hashable keys for pd.concat (pandas-dev#46608)

Author: twoertwein

pandas/_typing.py

@@ -73,6 +73,7 @@
 else:
     npt: Any = None
 
+HashableT = TypeVar("HashableT", bound=Hashable)
 
 # array-like
 

pandas/core/reshape/concat.py

@@ -18,7 +18,10 @@
 
 import numpy as np
 
-from pandas._typing import Axis
+from pandas._typing import (
+    Axis,
+    HashableT,
+)
 from pandas.util._decorators import (
     cache_readonly,
     deprecate_nonkeyword_arguments,
@@ -62,7 +65,7 @@
 
 @overload
 def concat(
-    objs: Iterable[DataFrame] | Mapping[Hashable, DataFrame],
+    objs: Iterable[DataFrame] | Mapping[HashableT, DataFrame],
     axis: Literal[0, "index"] = ...,
     join: str = ...,
     ignore_index: bool = ...,
@@ -78,7 +81,7 @@ def concat(
 
 @overload
 def concat(
-    objs: Iterable[Series] | Mapping[Hashable, Series],
+    objs: Iterable[Series] | Mapping[HashableT, Series],
     axis: Literal[0, "index"] = ...,
     join: str = ...,
     ignore_index: bool = ...,
@@ -94,7 +97,7 @@ def concat(
 
 @overload
 def concat(
-    objs: Iterable[NDFrame] | Mapping[Hashable, NDFrame],
+    objs: Iterable[NDFrame] | Mapping[HashableT, NDFrame],
     axis: Literal[0, "index"] = ...,
     join: str = ...,
     ignore_index: bool = ...,
@@ -110,7 +113,7 @@ def concat(
 
 @overload
 def concat(
-    objs: Iterable[NDFrame] | Mapping[Hashable, NDFrame],
+    objs: Iterable[NDFrame] | Mapping[HashableT, NDFrame],
     axis: Literal[1, "columns"],
     join: str = ...,
     ignore_index: bool = ...,
@@ -126,7 +129,7 @@ def concat(
 
 @overload
 def concat(
-    objs: Iterable[NDFrame] | Mapping[Hashable, NDFrame],
+    objs: Iterable[NDFrame] | Mapping[HashableT, NDFrame],
     axis: Axis = ...,
     join: str = ...,
     ignore_index: bool = ...,
@@ -142,7 +145,7 @@ def concat(
 
 @deprecate_nonkeyword_arguments(version=None, allowed_args=["objs"])
 def concat(
-    objs: Iterable[NDFrame] | Mapping[Hashable, NDFrame],
+    objs: Iterable[NDFrame] | Mapping[HashableT, NDFrame],
     axis: Axis = 0,
     join: str = "outer",
     ignore_index: bool = False,
@@ -367,7 +370,7 @@ class _Concatenator:
 
     def __init__(
         self,
-        objs: Iterable[NDFrame] | Mapping[Hashable, NDFrame],
+        objs: Iterable[NDFrame] | Mapping[HashableT, NDFrame],
         axis=0,
         join: str = "outer",
         keys=None,