TYP: get_indexer returns ndarray[intp]

pandas/core/indexes/base.py

@@ -3396,7 +3396,7 @@ def get_loc(self, key, method=None, tolerance=None):
     @final
     def get_indexer(
         self, target, method=None, limit=None, tolerance=None
-    ) -> np.ndarray:
+    ) -> np.ndarray[np.intp]:
 
         method = missing.clean_reindex_fill_method(method)
         target = ensure_index(target)
@@ -3421,7 +3421,7 @@ def get_indexer(
 
     def _get_indexer(
         self, target: Index, method=None, limit=None, tolerance=None
-    ) -> np.ndarray:
+    ) -> np.ndarray[np.intp]:
         if tolerance is not None:
             tolerance = self._convert_tolerance(tolerance, target)
 
@@ -5384,6 +5384,18 @@ def get_indexer_for(self, target, **kwargs):
         indexer, _ = self.get_indexer_non_unique(target)
         return indexer
 
+    @overload
+    def _get_indexer_non_comparable(
+        self, target: Index, method, unique: Literal[True] = ...
+    ) -> np.ndarray[np.intp]:
+        ...
+
+    @overload
+    def _get_indexer_non_comparable(
+        self, target: Index, method, unique: Literal[False] = ...
+    ) -> Tuple[np.ndarray[np.intp], np.ndarray[np.intp]]:
+        ...
+
     @final
     def _get_indexer_non_comparable(self, target: Index, method, unique: bool = True):
         """

pandas/core/indexes/category.py

@@ -3,6 +3,7 @@
     Hashable,
     List,
     Optional,
+    Tuple,
 )
 import warnings
 
@@ -484,19 +485,23 @@ def _maybe_cast_indexer(self, key) -> int:
 
     def _get_indexer(
         self, target: Index, method=None, limit=None, tolerance=None
-    ) -> np.ndarray:
+    ) -> np.ndarray[np.intp]:
 
         if self.equals(target):
             return np.arange(len(self), dtype="intp")
 
         return self._get_indexer_non_unique(target._values)[0]
 
     @Appender(_index_shared_docs["get_indexer_non_unique"] % _index_doc_kwargs)
-    def get_indexer_non_unique(self, target):
+    def get_indexer_non_unique(
+        self, target
+    ) -> Tuple[np.ndarray[np.intp], np.ndarray[np.intp]]:
         target = ibase.ensure_index(target)
         return self._get_indexer_non_unique(target._values)
 
-    def _get_indexer_non_unique(self, values: ArrayLike):
+    def _get_indexer_non_unique(
+        self, values: ArrayLike
+    ) -> Tuple[np.ndarray[np.intp], np.ndarray[np.intp]]:
         """
         get_indexer_non_unique but after unrapping the target Index object.
         """
@@ -515,7 +520,7 @@ def _get_indexer_non_unique(self, values: ArrayLike):
             codes = self.categories.get_indexer(values)
 
         indexer, missing = self._engine.get_indexer_non_unique(codes)
-        return ensure_platform_int(indexer), missing
+        return ensure_platform_int(indexer), ensure_platform_int(missing)
 
     @doc(Index._convert_list_indexer)
     def _convert_list_indexer(self, keyarr):

pandas/core/indexes/interval.py

@@ -700,7 +700,7 @@ def _get_indexer(
         method: Optional[str] = None,
         limit: Optional[int] = None,
         tolerance: Optional[Any] = None,
-    ) -> np.ndarray:
+    ) -> np.ndarray[np.intp]:
 
         if isinstance(target, IntervalIndex):
             # equal indexes -> 1:1 positional match
@@ -732,7 +732,9 @@ def _get_indexer(
         return ensure_platform_int(indexer)
 
     @Appender(_index_shared_docs["get_indexer_non_unique"] % _index_doc_kwargs)
-    def get_indexer_non_unique(self, target: Index) -> Tuple[np.ndarray, np.ndarray]:
+    def get_indexer_non_unique(
+        self, target: Index
+    ) -> Tuple[np.ndarray[np.intp], np.ndarray[np.intp]]:
         target = ensure_index(target)
 
         if isinstance(target, IntervalIndex) and not self._should_compare(target):
@@ -751,7 +753,9 @@ def get_indexer_non_unique(self, target: Index) -> Tuple[np.ndarray, np.ndarray]
 
         return ensure_platform_int(indexer), ensure_platform_int(missing)
 
-    def _get_indexer_pointwise(self, target: Index) -> Tuple[np.ndarray, np.ndarray]:
+    def _get_indexer_pointwise(
+        self, target: Index
+    ) -> Tuple[np.ndarray[np.intp], np.ndarray[np.intp]]:
         """
         pointwise implementation for get_indexer and get_indexer_non_unique.
         """

pandas/core/indexes/multi.py

@@ -2672,7 +2672,7 @@ def _get_partial_string_timestamp_match_key(self, key):
 
     def _get_indexer(
         self, target: Index, method=None, limit=None, tolerance=None
-    ) -> np.ndarray:
+    ) -> np.ndarray[np.intp]:
 
         # empty indexer
         if not len(target):

pandas/core/indexes/range.py

@@ -395,7 +395,9 @@ def get_loc(self, key, method=None, tolerance=None):
             raise KeyError(key)
         return super().get_loc(key, method=method, tolerance=tolerance)
 
-    def _get_indexer(self, target: Index, method=None, limit=None, tolerance=None):
+    def _get_indexer(
+        self, target: Index, method=None, limit=None, tolerance=None
+    ) -> np.ndarray[np.intp]:
         if com.any_not_none(method, tolerance, limit):
             return super()._get_indexer(
                 target, method=method, tolerance=tolerance, limit=limit