From 319d54abcfe5e4af34316fa47b68ab25e824a560 Mon Sep 17 00:00:00 2001
From: Patrick Kidger <33688385+patrick-kidger@users.noreply.github.com>
Date: Tue, 30 May 2023 12:30:07 -0700
Subject: [PATCH] Avoid __builtins__ getting added as a key

---
 jaxtyping/array_types.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/jaxtyping/array_types.py b/jaxtyping/array_types.py
index 45cc969..489efbe 100644
--- a/jaxtyping/array_types.py
+++ b/jaxtyping/array_types.py
@@ -123,7 +123,8 @@ def _check_dims(
                 return False
         elif type(cls_dim) is _SymbolicDim:
             try:
-                eval_size = eval(cls_dim.expr, single_memo)
+                # Make a copy to avoid `__builtins__` getting added as a key.
+                eval_size = eval(cls_dim.expr, single_memo.copy())
             except NameError as e:
                 raise NameError(
                     f"Cannot process symbolic dimension '{cls_dim.expr}' as some "