Backport 52621:

Bug #1588287: fix invalid assertion for `1,2` in debug builds.

Lib/test/test_grammar.py

@@ -709,6 +709,7 @@ x = {'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5, 'six': 6}
 
 x = `x`
 x = `1 or 2 or 3`
+x = `1,2`
 x = x
 x = 'x'
 x = 123

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 2.5.1c1?
 Core and builtins
 -----------------
 
+- Bug #1588287: fix invalid assertion for `1,2` in debug builds.
+
 - Bug #1576657: when setting a KeyError for a tuple key, make sure that
   the tuple isn't used as the "exception arguments tuple".
 

Python/ast.c

@@ -538,6 +538,7 @@ seq_for_testlist(struct compiling *c, const node *n)
 	   || TYPE(n) == listmaker
 	   || TYPE(n) == testlist_gexp
 	   || TYPE(n) == testlist_safe
+	   || TYPE(n) == testlist1
 	   );
 
     seq = asdl_seq_new((NCH(n) + 1) / 2, c->c_arena);