From 5ee5dcb6d1e8fcb5f87bad9a930bb9f5e21f6073 Mon Sep 17 00:00:00 2001
From: hauntsaninja <hauntsaninja@gmail.com>
Date: Wed, 7 Jun 2023 21:32:58 -0700
Subject: [PATCH] Fix crash when indexing TypedDict with empty key

Fixes #15389
---
 mypy/messages.py                    |  3 ++-
 test-data/unit/check-typeddict.test | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/mypy/messages.py b/mypy/messages.py
index a732d612123c..cb95fb1c0bde 100644
--- a/mypy/messages.py
+++ b/mypy/messages.py
@@ -2989,8 +2989,9 @@ def _real_quick_ratio(a: str, b: str) -> float:
 
 
 def best_matches(current: str, options: Collection[str], n: int) -> list[str]:
+    if not current:
+        return []
     # narrow down options cheaply
-    assert current
     options = [o for o in options if _real_quick_ratio(current, o) > 0.75]
     if len(options) >= 50:
         options = [o for o in options if abs(len(o) - len(current)) <= 1]
diff --git a/test-data/unit/check-typeddict.test b/test-data/unit/check-typeddict.test
index 970dc05b488d..fc487d2d553d 100644
--- a/test-data/unit/check-typeddict.test
+++ b/test-data/unit/check-typeddict.test
@@ -2873,3 +2873,15 @@ foo({"foo": {"e": "foo"}})  # E: Type of TypedDict is ambiguous, none of ("A", "
                             # E: Argument 1 to "foo" has incompatible type "Dict[str, Dict[str, str]]"; expected "Union[A, B]"
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]
+
+[case testTypedDictMissingEmptyKey]
+from typing_extensions import TypedDict
+
+class A(TypedDict):
+    my_attr_1: str
+    my_attr_2: int
+
+d: A
+d['']  # E: TypedDict "A" has no key ""
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-typeddict.pyi]