From 10231d89d76cb467729fb7391c6a80938d6c5f76 Mon Sep 17 00:00:00 2001
From: Andi Albrecht <albrecht.andi@gmail.com>
Date: Wed, 30 Sep 2020 15:15:56 +0200
Subject: Fix an issue with negative indexes causing IndexError in some cases.

---
 sqlparse/engine/grouping.py | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'sqlparse/engine')

diff --git a/sqlparse/engine/grouping.py b/sqlparse/engine/grouping.py
index e895ce0..fd1b18d 100644
--- a/sqlparse/engine/grouping.py
+++ b/sqlparse/engine/grouping.py
@@ -432,6 +432,8 @@ def _group(tlist, cls, match,
     pidx, prev_ = None, None
     for idx, token in enumerate(list(tlist)):
         tidx = idx - tidx_offset
+        if tidx < 0:  # tidx shouldn't get negative
+            continue
 
         if token.is_whitespace:
             continue
-- 
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