From 5d2ef0c1daf3d44db1acea0d201712a7b45875ea Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sun, 27 Jun 2021 12:24:24 -0700
Subject: regex-from-trie: correctly handle empty trie.

* filter.c (regex_from_trie): An empty trie matches nothing,
so we must return the t regex syntax (match nothing), not
nil (match empty string). A hash-based trie matches nothing
if it is empty; but if it has user data, then it matches
the empty string.

* tests/015/trie.tl: Test cases added.
---
 tests/015/trie.tl | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'tests/015')

diff --git a/tests/015/trie.tl b/tests/015/trie.tl
index de88a797..c145c060 100644
--- a/tests/015/trie.tl
+++ b/tests/015/trie.tl
@@ -52,3 +52,7 @@
 (mvtest
   (build (each ((d dat)) (add [rx1 d]))) dat
   (build (each ((n ndt)) (add [rx1 n]))) (repeat '(nil) (len dat)))
+
+(mtest
+  (regex-from-trie (make-trie)) t
+  (regex-from-trie (trie-compress (make-trie))) t)
-- 
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