$ may end any alternative in a pattern, not only the last

mvzr refuses $ anywhere but at the very end, so /h$|zz/ and Edit ,x/r$|pi/
were bad patterns while /zz|h$/ worked. Its matcher already ends an
alternative at .end, so a build-time patch, anchor-checked like the group
one, lets $ stand before | and ). The upstream report is in
docs/mvzr-group-backtrack.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/regexp.zig b/src/regexp.zig
index 97e3dc91..64e1d75a 100644
--- a/src/regexp.zig
+++ b/src/regexp.zig
@@ -258,3 +258,20 @@ test "a repeat inside a group gives back to what follows the group" {
         try std.testing.expectEqual(c.end, m.end);
     }
 }
+
+test "`$` may end any alternative, not only the last" {
+    const Case = struct { pat: []const u8, text: []const u8, start: usize, end: usize };
+    for ([_]Case{
+        .{ .pat = "h$|zz", .text = "xh", .start = 1, .end = 2 },
+        .{ .pat = "zz|h$", .text = "xh", .start = 1, .end = 2 },
+        .{ .pat = "h$|zz", .text = "hx zz", .start = 3, .end = 5 },
+        .{ .pat = "(h$|zz)", .text = "xh", .start = 1, .end = 2 },
+    }) |c| {
+        var rx = try Regex.compile(c.pat);
+        const m = (try rx.find(c.text, 0, c.text.len, c.text.len)).?;
+        try std.testing.expectEqual(c.start, m.start);
+        try std.testing.expectEqual(c.end, m.end);
+    }
+    var only = try Regex.compile("h$|zz");
+    try std.testing.expectEqual(null, try only.find("hx", 0, 2, 2));
+}