From 0a01fe2bc6748b5fa2b03cebdcaae0e655501ad4 Mon Sep 17 00:00:00 2001
From: Jan Bessai <jan.bessai@tu-dortmund.de>
Date: Fri, 2 May 2025 18:17:28 +0200
Subject: [PATCH] std.zig.Parse: fix and test off-by one in unreserveNode

---
 lib/std/zig/Parse.zig | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/lib/std/zig/Parse.zig b/lib/std/zig/Parse.zig
index facb74a006b5389a61bcc6a089234028fa0b1128..106b07f5ed058ec43231a5f1f4e5752ab2d6a8dc 100644
--- a/lib/std/zig/Parse.zig
+++ b/lib/std/zig/Parse.zig
@@ -92,7 +92,7 @@ fn reserveNode(p: *Parse, tag: Ast.Node.Tag) !usize {
 }
 
 fn unreserveNode(p: *Parse, node_index: usize) void {
-    if (p.nodes.len == node_index) {
+    if (p.nodes.len == node_index + 1) {
         p.nodes.resize(p.gpa, p.nodes.len - 1) catch unreachable;
     } else {
         // There is zombie node left in the tree, let's make it as inoffensive as possible
@@ -3417,3 +3417,22 @@ const Token = std.zig.Token;
 test {
     _ = @import("parser_test.zig");
 }
+
+test "unreserving a freshly reserved AST node must not create zombies" {
+    const gpa = std.testing.allocator;
+    var parser: Parse = .{
+        .gpa = gpa,
+        .nodes = .empty,
+        .errors = .empty,
+        .extra_data = .empty,
+        .scratch = .empty,
+        .source = "",
+        .tok_i = 0,
+        .tokens = undefined,
+        .recover = false,
+    };
+    defer parser.nodes.deinit(gpa);
+    const last = try parser.reserveNode(.@"try");
+    parser.unreserveNode(last);
+    try std.testing.expectEqual(parser.nodes.len, 0);
+}
-- 
2.54.0