From 63884d2efa6dc9993e14595a472aaf54330ac97a Mon Sep 17 00:00:00 2001
From: Zach Laine <whatwasthataddress@gmail.com>
Date: Thu, 22 Feb 2024 00:09:29 -0600
Subject: [PATCH] Fix an error in seq_parser when a non-attribute parser fails
 internally, after the successful parse of an adjacent attribute-generating
 parser.  Since the non-attribute parser points to the same spot in the output
 tuple, if the non-attribute parser fails internally, it is likely to do
 "out_attr = decltype(out_attr)()", which erases the previous seuccessfully
 generated attribute.

---
 include/boost/parser/parser.hpp | 6 +++++-
 test/parser.cpp                 | 7 +++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index b8bc9d68..ec83f7a1 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -3914,10 +3914,11 @@ namespace boost { namespace parser {
                                last,
                                &context,
                                &skip,
-                               flags,
+                               flags_ = flags,
                                &success,
                                &retval](auto const &
                                             parser_index_merged_and_backtrack) {
+                auto flags = flags_;
                 using namespace literals;
                 detail::skip(first, last, skip, flags);
                 if (!success) // Someone earlier already failed...
@@ -3969,6 +3970,9 @@ namespace boost { namespace parser {
                     container<std::decay_t<decltype(out)>>;
                 constexpr bool attr_container = container<attr_t>;
 
+                if constexpr (detail::is_nope_v<attr_t>)
+                    flags = detail::disable_attrs(flags);
+
                 if constexpr (
                     (out_container == attr_container &&
                      !was_merged_into_adjacent_container) ||
diff --git a/test/parser.cpp b/test/parser.cpp
index 03691c69..3dc2faf9 100644
--- a/test/parser.cpp
+++ b/test/parser.cpp
@@ -2167,6 +2167,13 @@ TEST(parser, combined_seq_and_or)
             EXPECT_EQ(chars, "xyz");
         }
     }
+
+    {
+        constexpr auto parser = int_ >> -(lit('a') | 'b');
+        auto result = parse("34b", parser);
+        EXPECT_TRUE(result);
+        EXPECT_EQ(*result, 34);
+    }
 }
 
 TEST(parser, eol_)