update CI from macos-13 to macos-15

MacOS 13 is retired in github actions, see
https://github.com/actions/runner-images/issues/13046

.github/workflows/macos-15.yml

@@ -1,4 +1,4 @@
-name: macos-13 - Clang 14
+name: macos-15 - Clang
 
 on:
   push:
@@ -14,9 +14,9 @@ jobs:
   build:
     strategy:
       matrix:
-        cxx_std: [17]
+        cxx_std: [17, 20]
 
-    runs-on: macos-13
+    runs-on: macos-15
 
     steps:
       - uses: actions/checkout@v4

include/boost/parser/error_handling.hpp

@@ -90,6 +90,9 @@ namespace boost { namespace parser {
         os << ":\n";
 
         std::string underlining(std::distance(position.line_start, it), ' ');
+        std::transform(position.line_start, it,
+            underlining.begin(),
+            [](auto c) { return c == '\t' ? '\t' : ' ';});
         detail::trace_input(os, position.line_start, it, false, 1u << 31);
         if (it == last) {
             os << '\n' << underlining << "^\n";

include/boost/parser/parser.hpp

@@ -3529,7 +3529,9 @@ namespace boost { namespace parser {
                 else
                     use_parser.first_ = prev_first;
             };
-            detail::hl::for_each(parsers_, try_parser); // TODO: -> fold-expr
+            std::apply([&try_parser](auto&&... args) {
+                ((try_parser(args)), ...);
+            }, parsers_);
 
             if (!done)
                 success = false;
@@ -4562,7 +4564,7 @@ namespace boost { namespace parser {
                     using just_out = detail::remove_cv_ref_t<decltype(out)>;
                     if constexpr (detail::is_nope_v<attr_t>) {
                         // nothing to do
-                    } if constexpr (
+                    } else if constexpr (
                         (!out_container ||
                          !std::is_same_v<just_x, just_out>) &&
                         std::is_assignable_v<just_out &, just_x &&> &&
@@ -4578,7 +4580,9 @@ namespace boost { namespace parser {
 
             auto const parsers_and_indices =
                 detail::hl::zip(parsers_, indices, merged, backtracking{});
-            detail::hl::for_each(parsers_and_indices, use_parser);
+            std::apply([&use_parser](auto&&... args) {
+                ((use_parser(args)), ...);
+            }, parsers_and_indices);
         }
 
         template<bool AllowBacktracking, typename Parser>
@@ -7635,9 +7639,10 @@ namespace boost { namespace parser {
 
             auto const prev_first = first;
 
-            auto append = [&retval,
+            std::string temp;
+            auto append = [&temp,
                            gen_attrs = detail::gen_attrs(flags)](auto & ctx) {
-                detail::move_back(retval, _attr(ctx), gen_attrs);
+                detail::move_back(temp, _attr(ctx), gen_attrs);
             };
 
             auto quote_ch = [&]() {
@@ -7695,7 +7700,10 @@ namespace boost { namespace parser {
                 detail::disable_skip(flags),
                 success);
 
-            if (!success) {
+            if (success) {
+                if (detail::gen_attrs(flags))
+                    detail::assign(retval, std::move(temp));
+            } else {
                 retval = Attribute();
                 first = prev_first;
             }
@@ -8521,9 +8529,9 @@ namespace boost { namespace parser {
     template<typename SwitchValue, typename OrParser>
     struct switch_parser
     {
-        switch_parser() {}
-        switch_parser(SwitchValue switch_value) : switch_value_(switch_value) {}
-        switch_parser(SwitchValue switch_value, OrParser or_parser) :
+        constexpr switch_parser() {}
+        constexpr switch_parser(SwitchValue switch_value) : switch_value_(switch_value) {}
+        constexpr switch_parser(SwitchValue switch_value, OrParser or_parser) :
             switch_value_(switch_value), or_parser_(or_parser)
         {}
 

test/github_issues.cpp

@@ -501,6 +501,62 @@ void github_issue_285()
     BOOST_TEST(result.value().get() != nullptr);
 }
 
+void github_pr_290()
+{
+    namespace bp = boost::parser;
+
+    auto const pTest = bp::lit("TEST:") > -bp::quoted_string;
+
+    auto result = bp::parse("TEST: \"foo\"", pTest, bp::blank);
+    BOOST_TEST(result);
+    BOOST_TEST(*result == "foo");
+}
+
+namespace github_pr_297_ {
+    namespace bp = boost::parser;
+    constexpr auto bar_required_f = [](auto& ctx) -> bool {
+        const bool& argument = bp::_p<0>(ctx);
+        return argument;
+    };
+    constexpr bp::rule<struct foobar_parser_tag> foobar_parser = "foobar_parser";
+    constexpr auto foobar_parser_def =
+        bp::lit("foo")
+        >> bp::switch_(bar_required_f)
+            (true, bp::lit("bar"))
+            (false, -bp::lit("bar"));
+    BOOST_PARSER_DEFINE_RULES(foobar_parser);
+}
+
+void github_pr_297()
+{
+    namespace bp = boost::parser;
+    using namespace github_pr_297_;
+
+    {
+        const bool bar_required = true;
+        const bool result =
+            bp::parse("foo bar", foobar_parser.with(bar_required), bp::blank);
+        BOOST_TEST(result);
+    }
+    {
+        const bool bar_required = true;
+        const bool result =
+            bp::parse("foo", foobar_parser.with(bar_required), bp::blank);
+        BOOST_TEST(!result);
+    }
+    {
+        const bool bar_required = false;
+        const bool result =
+            bp::parse("foo bar", foobar_parser.with(bar_required), bp::blank);
+        BOOST_TEST(result);
+    }
+    {
+        const bool bar_required = false;
+        const bool result =
+            bp::parse("foo", foobar_parser.with(bar_required), bp::blank);
+        BOOST_TEST(result);
+    }
+}
 
 int main()
 {
@@ -516,5 +572,7 @@ int main()
     github_issue_268();
     github_issue_279();
     github_issue_285();
+    github_pr_290();
+    github_pr_297();
     return boost::report_errors();
 }