fixes to fileinput (#1218)

- Correct incorrect return type for hook_encoded
- Add PathLike support
- Add some missing types
- Remove incorrect use of AnyStr

stdlib/3/fileinput.pyi

@@ -1,4 +1,13 @@
-from typing import Iterable, Callable, IO, AnyStr, Generic, Any, Union, Iterator
+from typing import Iterable, Callable, IO, AnyStr, Generic, Any, Union, Iterator, Optional
+
+import os
+import sys
+
+if sys.version_info >= (3, 6):
+    _Path = Union[str, bytes, os.PathLike[Any]]
+else:
+    _Path = Union[str, bytes]
+_Opener = Callable[[_Path, str], IO[AnyStr]]
 
 
 def input(
@@ -20,12 +29,12 @@ def isstdin() -> bool: ...
 class FileInput(Iterable[AnyStr], Generic[AnyStr]):
     def __init__(
         self,
-        files: Union[str, Iterable[str]]=None,
-        inplace: bool=...,
-        backup: str=...,
-        bufsize: int=...,
-        mode: str=...,
-        openhook: Callable[[str, str], IO[AnyStr]]=...
+        files: Union[None, _Path, Iterable[_Path]] = ...,
+        inplace: bool = ...,
+        backup: str = ...,
+        bufsize: int = ...,
+        mode: str = ...,
+        openhook: _Opener[AnyStr] = ...
     ) -> None: ...
 
     def __del__(self) -> None: ...
@@ -34,7 +43,7 @@ class FileInput(Iterable[AnyStr], Generic[AnyStr]):
     def __exit__(self, type: Any, value: Any, traceback: Any) -> None: ...
     def __iter__(self) -> Iterator[AnyStr]: ...
     def __next__(self) -> AnyStr: ...
-    def __getitem__(self, i) -> AnyStr: ...
+    def __getitem__(self, i: int) -> AnyStr: ...
     def nextfile(self) -> None: ...
     def readline(self) -> AnyStr: ...
     def filename(self) -> str: ...
@@ -44,5 +53,5 @@ class FileInput(Iterable[AnyStr], Generic[AnyStr]):
     def isfirstline(self) -> bool: ...
     def isstdin(self) -> bool: ...
 
-def hook_compressed(filename: str, mode: str) -> IO[AnyStr]: ...
-def hook_encoded(encoding: str) -> IO[AnyStr]: ...
+def hook_compressed(filename: _Path, mode: str) -> IO[Any]: ...
+def hook_encoded(encoding: str, errors: Optional[str] = ...) -> _Opener[Any]: ...