From 8d98960bedf8b062be11ea96a5de37236975a5e6 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Wed, 2 Feb 2022 20:17:48 -0800
Subject: [PATCH 1/2] add reveal_type

---
 typing_extensions/CHANGELOG                   |  1 +
 typing_extensions/README.rst                  |  4 ++++
 .../src/test_typing_extensions.py             |  7 ++++++
 typing_extensions/src/typing_extensions.py    | 23 +++++++++++++++++++
 4 files changed, 35 insertions(+)

diff --git a/typing_extensions/CHANGELOG b/typing_extensions/CHANGELOG
index 026ba598..6af2879b 100644
--- a/typing_extensions/CHANGELOG
+++ b/typing_extensions/CHANGELOG
@@ -1,5 +1,6 @@
 # Release 4.x.x
 
+- Add `reveal_type`. Backport from bpo-46414.
 - `Annotated` can now wrap `ClassVar` and `Final`. Backport from
   bpo-46491. Patch by Gregory Beauregard (@GBeauregard).
 - Add missed `Required` and `NotRequired` to `__all__`. Patch by
diff --git a/typing_extensions/README.rst b/typing_extensions/README.rst
index d5d4128f..18c09f97 100644
--- a/typing_extensions/README.rst
+++ b/typing_extensions/README.rst
@@ -39,6 +39,10 @@ This module currently contains the following:
 
   - ``NotRequired`` (see PEP 655)
   - ``Required`` (see PEP 655)
+
+- In ``typing`` since Python 3.11
+
+  - ``reveal_type``
   - ``Self`` (see PEP 673)
 
 - In ``typing`` since Python 3.10
diff --git a/typing_extensions/src/test_typing_extensions.py b/typing_extensions/src/test_typing_extensions.py
index f92bb135..670a1c7f 100644
--- a/typing_extensions/src/test_typing_extensions.py
+++ b/typing_extensions/src/test_typing_extensions.py
@@ -22,6 +22,7 @@
 from typing_extensions import TypeAlias, ParamSpec, Concatenate, ParamSpecArgs, ParamSpecKwargs, TypeGuard
 from typing_extensions import Awaitable, AsyncIterator, AsyncContextManager, Required, NotRequired
 from typing_extensions import Protocol, runtime, runtime_checkable, Annotated, overload, final, is_typeddict
+from typing_extensions import reveal_type
 try:
     from typing_extensions import get_type_hints
 except ImportError:
@@ -2345,6 +2346,12 @@ def cached(self): ...
         self.assertIs(True, Methods.cached.__final__)
 
 
+class RevealTypeTests(BaseTestCase):
+    def test_reveal_type(self):
+        obj = object()
+        self.assertIs(obj, reveal_type(obj))
+
+
 class AllTests(BaseTestCase):
 
     def test_typing_extensions_includes_standard(self):
diff --git a/typing_extensions/src/typing_extensions.py b/typing_extensions/src/typing_extensions.py
index dab53d43..bd5197b3 100644
--- a/typing_extensions/src/typing_extensions.py
+++ b/typing_extensions/src/typing_extensions.py
@@ -77,6 +77,7 @@ def _check_generic(cls, parameters):
     'NewType',
     'overload',
     'Protocol',
+    'reveal_type',
     'runtime',
     'runtime_checkable',
     'Text',
@@ -2341,3 +2342,25 @@ class Movie(TypedDict):
 
     Required = _Required(_root=True)
     NotRequired = _NotRequired(_root=True)
+
+if hasattr(typing, "reveal_type"):
+    reveal_type = typing.reveal_type
+else:
+    def reveal_type(obj: T, /) -> T:
+        """Reveal the inferred type of a variable.
+
+        When a static type checker encounters a call to ``reveal_type()``,
+        it will emit the inferred type of the argument::
+
+            x: int = 1
+            reveal_type(x)
+
+        Running a static type checker (e.g., ``mypy``) on this example
+        will produce output similar to 'Revealed type is "builtins.int"'.
+
+        At runtime, the function prints the runtime type of the
+        argument and returns it unchanged.
+
+        """
+        print(f"Runtime type is {type(obj).__name__!r}", file=sys.stderr)
+        return obj

From 53d17885dd7af7856962dbe23232dd018831bf91 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Wed, 2 Feb 2022 20:24:20 -0800
Subject: [PATCH 2/2] fix pos-only arg

---
 typing_extensions/src/typing_extensions.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/typing_extensions/src/typing_extensions.py b/typing_extensions/src/typing_extensions.py
index 8480d9c9..b594e33f 100644
--- a/typing_extensions/src/typing_extensions.py
+++ b/typing_extensions/src/typing_extensions.py
@@ -2347,7 +2347,7 @@ class Movie(TypedDict):
 if hasattr(typing, "reveal_type"):
     reveal_type = typing.reveal_type
 else:
-    def reveal_type(obj: T, /) -> T:
+    def reveal_type(__obj: T) -> T:
         """Reveal the inferred type of a variable.
 
         When a static type checker encounters a call to ``reveal_type()``,
@@ -2363,8 +2363,8 @@ def reveal_type(obj: T, /) -> T:
         argument and returns it unchanged.
 
         """
-        print(f"Runtime type is {type(obj).__name__!r}", file=sys.stderr)
-        return obj
+        print(f"Runtime type is {type(__obj).__name__!r}", file=sys.stderr)
+        return __obj
 
 
 if hasattr(typing, 'dataclass_transform'):