From 2451f873f1e9acde672a8dc696325d4f6518217f Mon Sep 17 00:00:00 2001
From: kampersanda <shnsk.knd@gmail.com>
Date: Sun, 17 Sep 2023 13:30:37 +0900
Subject: [PATCH] add comment

---
 src/trie.rs    | 4 ++++
 tests/tests.rs | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/src/trie.rs b/src/trie.rs
index 189f471..59634e2 100644
--- a/src/trie.rs
+++ b/src/trie.rs
@@ -131,6 +131,10 @@ impl<T> Sparse<T> {
                     continue 'a;
                 }
             }
+            // If edges allow all label values from x00 to xFF, such unreachable instances can be
+            // created. However, this would not happen in trie-match because only string literals
+            // are allowed, and xFF will never appear.
+            // (See hogehoge)
             unreachable!("No unused base found");
         }
         (bases, checks, values)
diff --git a/tests/tests.rs b/tests/tests.rs
index 44e1f8a..f46d6f3 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -129,6 +129,11 @@ fn test_try_base_conflict() {
 // This test confirms that check[0] does not have an invalid value of zero.
 #[test]
 fn test_invalid_root_check() {
+    // [0] -x01-> [1]
+    //    \-x00-> [0] ? If check[0] is 0, such an invalid transition is possible.
+    //
+    //  base: [0, MAX]
+    // check: [0,   1]
     let f = |text| {
         trie_match! {
             match text {