From 5f5ad8a9f4fa129749444ab4b4957d2d0a888006 Mon Sep 17 00:00:00 2001
From: Samuel Colvin <s@muelcolvin.com>
Date: Fri, 7 Apr 2023 11:31:56 +0100
Subject: [PATCH] add comment

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

diff --git a/pydantic_core/core_schema.py b/pydantic_core/core_schema.py
index 7242392f7..8066e6a0d 100644
--- a/pydantic_core/core_schema.py
+++ b/pydantic_core/core_schema.py
@@ -3283,9 +3283,9 @@ def definition_reference_schema(
     return dict_not_none(type='definition-ref', schema_ref=schema_ref, metadata=metadata, serialization=serialization)
 
 
-MYPY: Literal[False] = False
-
-
+MYPY = False
+# See https://github.com/python/mypy/issues/14034 for details, in summary mypy is extremely slow to process this
+# union which kills performance not just for pydantic, but even for code using pydantic
 if not MYPY:
     CoreSchema = Union[
         AnySchema,