Swift: tweak location extractor using new concept

Author: redsun82

swift/extractor/infra/SwiftDispatcher.h

@@ -175,7 +175,7 @@ class SwiftDispatcher {
     CODEQL_ASSERT(found != store.end(), "createEntry called on non-fetched label");
     using Tag = ConcreteTrapTagOf<E>;
     auto label = TrapLabel<Tag>::unsafeCreateFromUntyped(found->second);
-    if constexpr (requires { locationExtractor.attachLocation(sourceManager, e, label); }) {
+    if constexpr (IsLocatable<E>) {
       locationExtractor.attachLocation(sourceManager, e, label);
     }
     return TrapClassOf<E>{label};

swift/extractor/infra/SwiftLocationExtractor.h

@@ -59,13 +59,11 @@ swift::SourceRange getSourceRange(const llvm::MutableArrayRef<Locatable>& locata
   auto endRange = getSourceRange(locatables.back());
   return {startRange.Start, endRange.End};
 }
-
-// default case, no location
-swift::SourceRange getSourceRange(const auto&) {
-  return {};
-}
 }  // namespace detail
 
+template <typename E>
+concept IsLocatable = requires(E e) { detail::getSourceRange(e); };
+
 class SwiftLocationExtractor {
  public:
   explicit SwiftLocationExtractor(TrapDomain& trap) : trap(trap) {}
@@ -75,13 +73,13 @@ class SwiftLocationExtractor {
 
   // Emits a Location TRAP entry and attaches it to a `Locatable` trap label
   void attachLocation(const swift::SourceManager& sourceManager,
-                      const auto& locatable,
+                      const IsLocatable auto& locatable,
                       TrapLabel<LocatableTag> locatableLabel) {
     attachLocationImpl(sourceManager, detail::getSourceRange(locatable), locatableLabel);
   }
 
   void attachLocation(const swift::SourceManager& sourceManager,
-                      const auto* locatable,
+                      const IsLocatable auto* locatable,
                       TrapLabel<LocatableTag> locatableLabel) {
     attachLocation(sourceManager, *locatable, locatableLabel);
   }