Fix comment matching for includes not on top of the file

See foonathan/standardese#83.

src/libclang/libclang_parser.cpp

@@ -489,7 +489,9 @@ std::unique_ptr<cpp_file> libclang_parser::do_parse(const cpp_entity_index& idx,
                 auto include =
                     cpp_include_directive::build(std::move(include_iter->file), include_iter->kind,
                                                  detail::get_cursor_name(cur).c_str());
-                context.comments.match(*include, include_iter->line);
+                context.comments.match(*include, include_iter->line,
+                                       false); // must not skip comments,
+                                               // includes are not reported in order
                 builder.add_child(std::move(include));
 
                 ++include_iter;

src/libclang/parse_functions.cpp

@@ -85,13 +85,17 @@ void detail::comment_context::match(cpp_entity& e, const CXCursor& cur) const
     match(e, line);
 }
 
-void detail::comment_context::match(cpp_entity& e, unsigned line) const
+void detail::comment_context::match(cpp_entity& e, unsigned line, bool skip_comments) const
 {
     // find comment
+    auto save = cur_;
     while (cur_ != end_ && cur_->line + 1 < line)
         ++cur_;
     if (cur_ != end_ && cur_->matches(e, line))
         e.set_comment(std::move(cur_++->comment));
+
+    if (!skip_comments)
+        cur_ = save;
 }
 
 namespace

src/libclang/parse_functions.hpp

@@ -48,7 +48,7 @@ namespace cppast
             // must be called for entities that want an associated comment
             // must be called *BEFORE* the children are added
             void match(cpp_entity& e, const CXCursor& cur) const;
-            void match(cpp_entity& e, unsigned line) const;
+            void match(cpp_entity& e, unsigned line, bool skip_comments = true) const;
 
         private:
             mutable pp_doc_comment* cur_;

test/cpp_preprocessor.cpp

@@ -279,6 +279,10 @@ g(h)
  i */
 using i = int;
 
+/// cstddef
+/// cstddef
+#include <cstddef>
+
 /// j
 /// j
 template <typename T/**/>
@@ -300,7 +304,15 @@ void j();
         return true;
     });
 
+    auto add = 0u;
     for (auto& comment : file->unmatched_comments())
-        REQUIRE(comment.content == "u");
-    REQUIRE((file->unmatched_comments().size() == 3u));
+    {
+        if (comment.content == "cstddef\ncstddef")
+            // happens if include parsing is not supported
+            // error is still going to be detected because if it is supported, the entity will be matched above
+            add = 1u;
+        else
+            REQUIRE(comment.content == "u");
+    }
+    REQUIRE((file->unmatched_comments().size() == 3u + add));
 }