From dc6144eeb45a5bf809df862887ae729bd330aee2 Mon Sep 17 00:00:00 2001
From: Zach Laine <whatwasthataddress@gmail.com>
Date: Fri, 31 Oct 2025 12:37:40 -0500
Subject: [PATCH] Correct tuple/struct confusion in the logic of the if
 constexpr chain in perm_parser.

Test case by Andreas Buhr.

Fixes #268.
---
 include/boost/parser/parser.hpp | 24 +++++++++-------
 test/github_issues.cpp          | 50 +++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 10 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index 5c58df3c..8cdea90c 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -3680,9 +3680,7 @@ namespace boost { namespace parser {
                 call(first, last, context, skip, flags, success, attr);
                 if (success)
                     detail::assign(retval, std::move(attr));
-            } else if constexpr (
-                detail::is_tuple<Attribute>{} ||
-                detail::is_struct_compatible_v<Attribute, result_t>) {
+            } else if constexpr (detail::is_tuple<Attribute>{}) {
                 call_impl(
                     first,
                     last,
@@ -3695,9 +3693,9 @@ namespace boost { namespace parser {
 
                 if (!success)
                     detail::assign(retval, Attribute());
-            } else if constexpr (detail::is_constructible_from_tuple_v<
-                                     Attribute,
-                                     result_t>) {
+            } else if constexpr (
+                detail::is_struct_compatible_v<Attribute, result_t> ||
+                detail::is_constructible_from_tuple_v<Attribute, result_t>) {
                 result_t temp_retval{};
                 call_impl(
                     first,
@@ -3710,10 +3708,16 @@ namespace boost { namespace parser {
                     indices);
 
                 if (success && detail::gen_attrs(flags)) {
-                    detail::assign(
-                        retval,
-                        detail::make_from_tuple<Attribute>(
-                            std::move(temp_retval)));
+                    if constexpr (detail::is_struct_compatible_v<
+                                      Attribute,
+                                      result_t>) {
+                        detail::assign(retval, temp_retval);
+                    } else {
+                        detail::assign(
+                            retval,
+                            detail::make_from_tuple<Attribute>(
+                                std::move(temp_retval)));
+                    }
                 }
             } else {
 #if 0 // TODO Seems incompatible with this parser.
diff --git a/test/github_issues.cpp b/test/github_issues.cpp
index f64beccb..be2497ca 100644
--- a/test/github_issues.cpp
+++ b/test/github_issues.cpp
@@ -344,6 +344,55 @@ void github_issue_248()
     }
 }
 
+namespace github_issue_268_ {
+    namespace bp = boost::parser;
+    constexpr bp::rule<struct name, std::string_view> name = "name";
+    auto name_def = bp::string_view[bp::lexeme[+(bp::lower | bp::upper | bp::digit | bp::char_("_"))]];
+    BOOST_PARSER_DEFINE_RULES(name)
+    constexpr bp::rule<struct qd_vec, std::vector<double>> qd_vec = "qd_vec";
+    auto qd_vec_def = bp::lit("\"") >> bp::double_ % (bp::lit(",") | (bp::lit("\"") >> bp::lit(",") >> bp::lit("\""))) >> bp::lit('\"');
+    BOOST_PARSER_DEFINE_RULES(qd_vec)
+    struct lu_table_template_1
+    {
+        std::vector<double> index_1;
+        std::string_view variable_1;
+    };
+    constexpr boost::parser::rule<struct lu_table_template_1_tag, lu_table_template_1> lu_table_template_1_rule = "lu_table_template_1";
+    auto lu_table_template_1_rule_def = (bp::lit("index_1") >> '(' >> qd_vec >> ')' >> ';') >> (bp::lit("variable_1") >> ':' >> name >> ';');
+    BOOST_PARSER_DEFINE_RULES(lu_table_template_1_rule)
+
+    constexpr boost::parser::rule<struct lu_table_template_1_permut_tag, lu_table_template_1> lu_table_template_1_permut_rule = "lu_table_template_1";
+    auto lu_table_template_1_permut_rule_def = (bp::lit("index_1") >> '(' >> qd_vec >> ')' >> ';') || (bp::lit("variable_1") >> ':' >> name >> ';');
+    BOOST_PARSER_DEFINE_RULES(lu_table_template_1_permut_rule)
+}
+
+void github_issue_268()
+{
+    namespace bp = boost::parser;
+    using namespace github_issue_268_;
+    std::string inputstring = "index_1 ( \"1\" ) ; variable_1 : bier;";
+
+    auto const def_result = bp::parse(
+        inputstring, lu_table_template_1_rule_def, bp::blank, bp::trace::off);
+    std::cout<< "seq_parser generates this type:\n" << typeid(def_result.value()).name() << std::endl;
+    BOOST_TEST(def_result);
+
+    auto const permut_def_result = bp::parse(
+        inputstring, lu_table_template_1_permut_rule_def, bp::blank, bp::trace::off);
+    std::cout<< "permut_parser generates this type:\n" << typeid(permut_def_result.value()).name() << std::endl;
+    BOOST_TEST(permut_def_result);
+
+    auto const result = bp::parse(
+        inputstring, lu_table_template_1_rule, bp::blank, bp::trace::off);
+    std::cout<< "seq_parser in rule generates this type:\n" << typeid(result.value()).name() << std::endl;
+    BOOST_TEST(result);
+
+    auto const permut_result = bp::parse(
+        inputstring, lu_table_template_1_permut_rule, bp::blank, bp::trace::off);
+    std::cout<< "permut_parser generates this type:\n" << typeid(permut_result.value()).name() << std::endl;
+    BOOST_TEST(permut_result);
+}
+
 void github_issue_279()
 {
     namespace bp = boost::parser;
@@ -373,6 +422,7 @@ int main()
     github_issue_209();
     github_issue_223();
     github_issue_248();
+    github_issue_268();
     github_issue_279();
     return boost::report_errors();
 }