Swift: implement ignoring of removed classes

swift/extractor/infra/SwiftTagTraits.h

@@ -9,25 +9,39 @@
 
 namespace codeql {
 
-// codegen goes with QL acronym convention (Sil instead of SIL), we need to remap it to Swift's
-// convention
-using SILBlockStorageTypeTag = SilBlockStorageTypeTag;
-using SILBoxTypeTag = SilBoxTypeTag;
-using SILFunctionTypeTag = SilFunctionTypeTag;
-using SILTokenTypeTag = SilTokenTypeTag;
-
 // OverloadSetRefExpr is collapsed with its only derived class OverloadedDeclRefExpr
 using OverloadSetRefExprTag = OverloadedDeclRefExprTag;
 
+// We don't really expect to see the following in extraction. Mapping these tags to void effectively
+// ignores all elements of that class (with a message).
+
+// only generated for code editing
+using CodeCompletionExprTag = void;
+using EditorPlaceholderExprTag = void;
+// not present after the Sema phase
+using ArrowExprTag = void;
+// experimental variadic generics, implemented only in the frontend for now, thus not compilable
+using PackExprTag = void;
+using PackTypeTag = void;
+using ReifyPackExprTag = void;
+using PackExpansionTypeTag = void;
+// Placeholder types appear in ambiguous types but are anyway transformed to UnresolvedType
+using PlaceholderTypeTag = void;
+// SIL types that cannot really appear in the frontend run
+using SILBlockStorageTypeTag = void;
+using SILBoxTypeTag = void;
+using SILFunctionTypeTag = void;
+using SILTokenTypeTag = void;
+
 #define MAP_TYPE_TO_TAG(TYPE, TAG)    \
   template <>                         \
   struct detail::ToTagFunctor<TYPE> { \
     using type = TAG;                 \
   }
 #define MAP_TAG(TYPE) MAP_TYPE_TO_TAG(swift::TYPE, TYPE##Tag)
-#define MAP_SUBTAG(TYPE, PARENT)                           \
-  MAP_TAG(TYPE);                                           \
-  static_assert(std::is_base_of_v<PARENT##Tag, TYPE##Tag>, \
+#define MAP_SUBTAG(TYPE, PARENT)                                                              \
+  MAP_TAG(TYPE);                                                                              \
+  static_assert(std::is_same_v<TYPE##Tag, void> || std::is_base_of_v<PARENT##Tag, TYPE##Tag>, \
                 #PARENT "Tag must be a base of " #TYPE "Tag");
 
 #define OVERRIDE_TAG(TYPE, TAG)               \

swift/extractor/translators/ExprTranslator.cpp

@@ -584,6 +584,7 @@ static int translatePropertyWrapperValueKind(swift::AppliedPropertyWrapperExpr::
       return 0;
   }
 }
+
 codeql::AppliedPropertyWrapperExpr ExprTranslator::translateAppliedPropertyWrapperExpr(
     const swift::AppliedPropertyWrapperExpr& expr) {
   auto entry = createExprEntry(expr);

swift/extractor/translators/TranslatorBase.h

@@ -62,10 +62,15 @@ DEFINE_TRANSLATE_CHECKER(TypeRepr, , )
 // superclasses by default and instead provide our own TBD default (using the exact type).
 // Moreover, if the implementation class has translate##CLASS##KIND (that uses generated C++
 // classes), for the class of for a parent thereof, we want to use that. We detect that by using the
-// type traits HasTranslate##CLASS##KIND defined above
+// type traits HasTranslate##CLASS##KIND defined above.
+// A special case is for explicitly ignored classes marked with void, which we should never
+// encounter.
 #define DEFINE_VISIT(KIND, CLASS, PARENT)                                            \
   void visit##CLASS##KIND(swift::CLASS##KIND* e) {                                   \
-    if constexpr (detail::HasTranslate##CLASS##KIND<CrtpSubclass>::value) {          \
+    if constexpr (std::is_same_v<CLASS##KIND##Tag, void>) {                          \
+      std::cerr << "Unexpected " #CLASS #KIND "\n";                                  \
+      return;                                                                        \
+    } else if constexpr (detail::HasTranslate##CLASS##KIND<CrtpSubclass>::value) {   \
       dispatcher.emit(static_cast<CrtpSubclass*>(this)->translate##CLASS##KIND(*e)); \
     } else if constexpr (detail::HasTranslate##PARENT<CrtpSubclass>::value) {        \
       dispatcher.emit(static_cast<CrtpSubclass*>(this)->translate##PARENT(*e));      \
@@ -105,9 +110,6 @@ class AstTranslatorBase : private swift::ASTVisitor<CrtpSubclass>,
 
 #define PATTERN(CLASS, PARENT) DEFINE_VISIT(Pattern, CLASS, PARENT)
 #include "swift/AST/PatternNodes.def"
-
-#define TYPEREPR(CLASS, PARENT) DEFINE_VISIT(TypeRepr, CLASS, PARENT)
-#include "swift/AST/TypeReprNodes.def"
 };
 
 // base class for our type visitor, getting a SwiftDispatcher member and define_visit emission for