From f1ad6c55fb3e03e0279e89ade66c86736e8d3edb Mon Sep 17 00:00:00 2001
From: wouter bolsterlee <wouter@bolsterl.ee>
Date: Tue, 30 Jun 2020 19:51:57 +0200
Subject: [PATCH] Use correct return type annotation for
 BaseException.with_traceback
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The return type of the BaseException.with_traceback() method [1] is not
specific enough. The return type is guaranteed to be of the same type as
‘self’, which is usually a subclass of BaseException.

In fact, .with_traceback() returns ‘self’:

    try:
        raise ValueError
    except Exception as exc:
        assert exc.with_traceback(None) is exc

Fix the annotation to reflect this using the self-type annotation
technique described in PEP484 [2], which is supported by (at least)
mypy [3].

[1] https://docs.python.org/3/library/exceptions.html#BaseException.with_traceback
[2] https://www.python.org/dev/peps/pep-0484/#annotating-instance-and-class-methods
[3] https://github.com/python/mypy/issues/1212
---
 stdlib/2/__builtin__.pyi  | 3 ++-
 stdlib/2and3/builtins.pyi | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/stdlib/2/__builtin__.pyi b/stdlib/2/__builtin__.pyi
index 24c93a18e857..650a19fa8a26 100644
--- a/stdlib/2/__builtin__.pyi
+++ b/stdlib/2/__builtin__.pyi
@@ -82,6 +82,7 @@ _T4 = TypeVar("_T4")
 _T5 = TypeVar("_T5")
 _TT = TypeVar("_TT", bound="type")
 _LT = TypeVar("_LT", bound=_SupportsLessThan)
+_TBE = TypeVar("_TBE", bound="BaseException")
 
 class object:
     __doc__: Optional[str]
@@ -1775,7 +1776,7 @@ class BaseException(object):
         def __getitem__(self, i: int) -> Any: ...
         def __getslice__(self, start: int, stop: int) -> Tuple[Any, ...]: ...
     if sys.version_info >= (3,):
-        def with_traceback(self, tb: Optional[TracebackType]) -> BaseException: ...
+        def with_traceback(self: _TBE, tb: Optional[TracebackType]) -> _TBE: ...
 
 class GeneratorExit(BaseException): ...
 class KeyboardInterrupt(BaseException): ...
diff --git a/stdlib/2and3/builtins.pyi b/stdlib/2and3/builtins.pyi
index 24c93a18e857..650a19fa8a26 100644
--- a/stdlib/2and3/builtins.pyi
+++ b/stdlib/2and3/builtins.pyi
@@ -82,6 +82,7 @@ _T4 = TypeVar("_T4")
 _T5 = TypeVar("_T5")
 _TT = TypeVar("_TT", bound="type")
 _LT = TypeVar("_LT", bound=_SupportsLessThan)
+_TBE = TypeVar("_TBE", bound="BaseException")
 
 class object:
     __doc__: Optional[str]
@@ -1775,7 +1776,7 @@ class BaseException(object):
         def __getitem__(self, i: int) -> Any: ...
         def __getslice__(self, start: int, stop: int) -> Tuple[Any, ...]: ...
     if sys.version_info >= (3,):
-        def with_traceback(self, tb: Optional[TracebackType]) -> BaseException: ...
+        def with_traceback(self: _TBE, tb: Optional[TracebackType]) -> _TBE: ...
 
 class GeneratorExit(BaseException): ...
 class KeyboardInterrupt(BaseException): ...