Fix prefix-suffix conflict due to insertion order of trailing slashes

When inserting route parameters with static suffixes, `matchit` checked
for conflicts between newly inserted suffixes and existing ones. It had
an explicit exception to allow a new suffix that only differed by an
extra trailing slash (e.g., `o/` vs existing `o`).

However, this check only evaluated one direction: if the *new* suffix
was longer than the *existing* suffix. If the routes were inserted in
the reverse order (e.g., `o/` inserted first, then `o` inserted second),
the router incorrectly flagged them as a prefix-suffix conflict.

This commit makes the trailing slash check bidirectional by adding an
`else` branch to verify if the *existing* suffix is the one with the
extra trailing slash, resolving the insertion order dependency.

Signed-off-by: Changyuan Lyu <changyuanl@google.com>

Author: Lencerf

src/tree.rs

@@ -223,6 +223,11 @@ impl<T> Node<T> {
                         if *common == *child.prefix && remaining == *b"/" {
                             extra_trailing_slash = true;
                         }
+                    } else {
+                        let (common, remaining) = child.prefix.split_at(suffix.len());
+                        if *common == **suffix && remaining == *b"/" {
+                            extra_trailing_slash = true;
+                        }
                     }
                 }
 

tests/insert.rs

@@ -260,7 +260,7 @@ fn prefix_suffix_conflict() {
         ("/x19/f{a}o", Ok(())),
         ("/x19/f{a}o/{*path}", Ok(())),
         ("/x20/f{a}o/{*path}", Ok(())),
-        ("/x20/f{a}o", Err(conflict("/x20/f{a}o/{*path}"))),
+        ("/x20/f{a}o", Ok(())),
     ])
     .run()
 }