SIL: Adjust isTypeMetadataForLayoutAccessible() to visit more lowered positions

Fixes part of swiftlang#67645, rdar://119267393

Author: slavapestov

lib/SIL/IR/SIL.cpp

@@ -256,6 +256,24 @@ static bool isTypeMetadataForLayoutAccessible(SILModule &M, SILType type) {
   if (type.is<AnyMetatypeType>())
     return true;
 
+  //   - pack expansion types
+  if (auto expansionType = type.getAs<PackExpansionType>()) {
+    auto patternType = SILType::getPrimitiveType(expansionType.getPatternType(),
+                                                 type.getCategory());
+    return isTypeMetadataForLayoutAccessible(M, patternType);
+  }
+
+  //   - lowered pack types
+  if (auto packType = type.getAs<SILPackType>()) {
+    for (auto eltType : packType.getElementTypes()) {
+      if (!isTypeMetadataForLayoutAccessible(
+              M, SILType::getPrimitiveAddressType(eltType)))
+        return false;
+    }
+
+    return true;
+  }
+
   // Otherwise, check that we can fetch the type metadata.
   return M.isTypeMetadataAccessible(type.getASTType());
 }