[Runtime] Skip types with pack parameters in LibPrespecialized.

We don't yet support pack parameters anyway, and `_buildDemanglingForGenericType` has trouble with them, so skip them altogether.

Author: mikeash

stdlib/public/runtime/LibPrespecialized.cpp

@@ -72,6 +72,20 @@ const LibPrespecializedData<InProcess> *swift::getLibPrespecializedData() {
   return SWIFT_LAZY_CONSTANT(findLibPrespecialized());
 }
 
+// Returns true if the type has any arguments that aren't plain types (packs or
+// unknown kinds).
+static bool hasNonTypeGenericArguments(const TypeContextDescriptor *description) {
+  auto generics = description->getGenericContext();
+  if (!generics)
+    return false;
+
+  for (auto param : generics->getGenericParams())
+    if (param.getKind() != GenericParamKind::Type)
+      return true;
+
+  return false;
+}
+
 static bool disableForValidation = false;
 
 Metadata *
@@ -84,6 +98,11 @@ swift::getLibPrespecializedMetadata(const TypeContextDescriptor *description,
   if (!data)
     return nullptr;
 
+  // We don't support types with pack parameters yet (and especially not types
+  // with unknown parameter kinds) so don't even try to look those up.
+  if (hasNonTypeGenericArguments(description))
+    return nullptr;
+
   Demangler dem;
   auto mangleNode = _buildDemanglingForGenericType(description, arguments, dem);
   if (mangleNode->getKind() != Node::Kind::Global) {