From bdda22a93a9280e50fe3b7a639edb515ef98a7dd Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Wed, 2 Feb 2022 21:53:23 -0800
Subject: [PATCH] add support for typing.reveal_type

---
 mypy/semanal.py                               |  4 ++--
 mypy/types.py                                 |  6 ++++++
 test-data/unit/check-expressions.test         | 16 ++++++++++++++++
 test-data/unit/lib-stub/typing.pyi            |  2 ++
 test-data/unit/lib-stub/typing_extensions.pyi |  2 ++
 5 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/mypy/semanal.py b/mypy/semanal.py
index 2d7c4c7e3d4c..876866963e6b 100644
--- a/mypy/semanal.py
+++ b/mypy/semanal.py
@@ -98,7 +98,7 @@
     CallableType, Overloaded, Instance, Type, AnyType, LiteralType, LiteralValue,
     TypeTranslator, TypeOfAny, TypeType, NoneType, PlaceholderType, TPDICT_NAMES, ProperType,
     get_proper_type, get_proper_types, TypeAliasType, TypeVarLikeType,
-    PROTOCOL_NAMES, TYPE_ALIAS_NAMES, FINAL_TYPE_NAMES, FINAL_DECORATOR_NAMES,
+    PROTOCOL_NAMES, TYPE_ALIAS_NAMES, FINAL_TYPE_NAMES, FINAL_DECORATOR_NAMES, REVEAL_TYPE_NAMES,
     is_named_instance,
 )
 from mypy.typeops import function_type, get_type_vars
@@ -3877,7 +3877,7 @@ def visit_call_expr(self, expr: CallExpr) -> None:
             expr.analyzed.line = expr.line
             expr.analyzed.column = expr.column
             expr.analyzed.accept(self)
-        elif refers_to_fullname(expr.callee, 'builtins.reveal_type'):
+        elif refers_to_fullname(expr.callee, REVEAL_TYPE_NAMES):
             if not self.check_fixed_args(expr, 1, 'reveal_type'):
                 return
             expr.analyzed = RevealExpr(kind=REVEAL_TYPE, expr=expr.args[0])
diff --git a/mypy/types.py b/mypy/types.py
index 1d7ab669a2d4..5aecb8194f9e 100644
--- a/mypy/types.py
+++ b/mypy/types.py
@@ -126,6 +126,12 @@
     'typing.Reversible',
 )
 
+REVEAL_TYPE_NAMES: Final = (
+    'builtins.reveal_type',
+    'typing.reveal_type',
+    'typing_extensions.reveal_type',
+)
+
 # A placeholder used for Bogus[...] parameters
 _dummy: Final[Any] = object()
 
diff --git a/test-data/unit/check-expressions.test b/test-data/unit/check-expressions.test
index a275de94c9be..543502e65115 100644
--- a/test-data/unit/check-expressions.test
+++ b/test-data/unit/check-expressions.test
@@ -1688,6 +1688,22 @@ main:1: note: Revealed type is "Any"
 def reveal_type(x: int) -> None: pass
 reveal_type("foo") # E: Argument 1 to "reveal_type" has incompatible type "str"; expected "int"
 
+[case testTypingRevealType]
+from typing import reveal_type
+from typing import reveal_type as show_me_the_type
+
+reveal_type(1) # N: Revealed type is "Literal[1]?"
+show_me_the_type(1) # N: Revealed type is "Literal[1]?"
+
+[case testTypingExtensionsRevealType]
+from typing_extensions import reveal_type
+from typing_extensions import reveal_type as show_me_the_type
+
+reveal_type(1) # N: Revealed type is "Literal[1]?"
+show_me_the_type(1) # N: Revealed type is "Literal[1]?"
+
+[builtins fixtures/tuple.pyi]
+
 [case testRevealTypeVar]
 reveal_type = 1
 1 + "foo" # E: Unsupported operand types for + ("int" and "str")
diff --git a/test-data/unit/lib-stub/typing.pyi b/test-data/unit/lib-stub/typing.pyi
index b9f1752aee1b..7283b47a96e7 100644
--- a/test-data/unit/lib-stub/typing.pyi
+++ b/test-data/unit/lib-stub/typing.pyi
@@ -47,3 +47,5 @@ class Sequence(Iterable[T_co]):
 class Mapping(Iterable[T], Generic[T, T_co]): pass
 
 def final(meth: T) -> T: pass
+
+def reveal_type(__obj: T) -> T: pass
diff --git a/test-data/unit/lib-stub/typing_extensions.pyi b/test-data/unit/lib-stub/typing_extensions.pyi
index 5b32449e71cf..7c6e14e404cd 100644
--- a/test-data/unit/lib-stub/typing_extensions.pyi
+++ b/test-data/unit/lib-stub/typing_extensions.pyi
@@ -44,3 +44,5 @@ class _TypedDict(Mapping[str, object]):
     def __delitem__(self, k: NoReturn) -> None: ...
 
 def TypedDict(typename: str, fields: Dict[str, Type[_T]], *, total: Any = ...) -> Type[dict]: ...
+
+def reveal_type(__obj: T) -> T: pass