Swift: use C++ entry style visitor in DeclVisitor

Author: redsun82

swift/codegen/schema.yml

@@ -19,7 +19,7 @@ File:
   name: string
 
 Locatable:
-  location: Location
+  location: Location?
 
 Location:
   file: File

swift/codegen/templates/cpp_classes.mustache

@@ -7,6 +7,7 @@
 #include <vector>
 
 #include "{{include_dir}}/{{trap_affix}}Label.h"
+#include "{{include_dir}}/{{trap_affix}}TagTraits.h"
 #include "./{{trap_affix}}Entries.h"
 
 namespace {{namespace}} {
@@ -54,5 +55,10 @@ struct {{name}}{{#final}} : Binding<{{name}}Tag>{{#bases}}, {{ref.name}}{{/bases
     {{/fields}}
   }
 };
+
+template <>
+struct detail::ToTrapClassFunctor<{{name}}Tag> {
+  using type = {{name}};
+};
 {{/classes}}
 }

swift/extractor/SwiftDispatcher.h

@@ -120,6 +120,27 @@ class SwiftDispatcher {
                    locatableLabel);
   }
 
+  // return `std::optional(fetchLabel(arg))` if arg converts to true, otherwise std::nullopt
+  template <typename Arg>
+  auto fetchOptionalLabel(Arg&& arg)
+      -> std::optional<decltype(fetchLabel(std::forward<Arg>(arg)))> {
+    if (arg) {
+      return fetchLabel(std::forward<Arg>(arg));
+    }
+    return std::nullopt;
+  }
+
+  // map `fetchLabel` on the iterable `arg`, returning a vector of all labels
+  template <typename Iterable>
+  auto fetchRepeatedLabels(Iterable&& arg) -> std::vector<decltype(fetchLabel(*arg.begin()))> {
+    std::vector<decltype(fetchLabel(*arg.begin()))> ret;
+    ret.reserve(arg.size());
+    for (const auto& e : arg) {
+      ret.push_back(fetchLabel(e));
+    }
+    return ret;
+  }
+
  private:
   // types to be supported by assignNewLabel/fetchLabel need to be listed here
   using Store = TrapLabelStore<swift::Decl,
@@ -147,7 +168,7 @@ class SwiftDispatcher {
     auto locLabel = createLabel<LocationTag>('{', fileLabel, "}:", startLine, ':', startColumn, ':',
                                              endLine, ':', endColumn);
     trap.emit(LocationsTrap{locLabel, fileLabel, startLine, startColumn, endLine, endColumn});
-    trap.emit(LocatablesTrap{locatableLabel, locLabel});
+    trap.emit(LocatableLocationsTrap{locatableLabel, locLabel});
   }
 
   template <typename Tag, typename... Ts>

swift/extractor/trap/TrapTagTraits.h

@@ -19,6 +19,10 @@ struct ToTagOverride : ToTagFunctor<T> {};
 // must be instantiated to map trap labels to the corresponding generated binding trap entry
 template <typename Label>
 struct ToBindingTrapFunctor;
+
+// must be instantiated to map trap tags to the corresponding generated trap class
+template <typename Tag>
+struct ToTrapClassFunctor;
 }  // namespace detail
 
 template <typename T>
@@ -30,4 +34,7 @@ using TrapLabelOf = TrapLabel<TrapTagOf<T>>;
 template <typename T>
 using BindingTrapOf = typename detail::ToBindingTrapFunctor<TrapLabelOf<T>>::type;
 
+template <typename T>
+using TrapClassOf = typename detail::ToTrapClassFunctor<TrapTagOf<T>>::type;
+
 }  // namespace codeql