Modify handling of SYCL special types to account for default construc…

…tor access specifier

clang/lib/Sema/SemaSYCL.cpp

@@ -3950,13 +3950,28 @@ class SyclKernelBodyCreator : public SyclKernelFieldHandler {
   }
 
   // Default inits the type, then calls the init-method in the body.
+  // A type may not have a public private default constructor as per its spec so
+  // typically the default constructor will be private and in such cases we must
+  // manually override the access specifier from private to public just for the
+  // duration of this default initialization.
   bool handleSpecialType(FieldDecl *FD, QualType Ty) {
+    const auto *RecordDecl = Ty->getAsCXXRecordDecl();
+    AccessSpecifier default_constructor_access;
+    CXXConstructorDecl *default_constructor;
+    std::for_each(RecordDecl->ctor_begin(), RecordDecl->ctor_end(),
+                  [&](auto elem) {
+                    if (elem->isDefaultConstructor()) {
+                      default_constructor_access = elem->getAccess();
+                      elem->setAccess(AS_public);
+                      default_constructor = elem;
+                    }
+                  });
+
     addFieldInit(FD, Ty, std::nullopt,
                  InitializationKind::CreateDefault(KernelCallerSrcLoc));
-
+    default_constructor->setAccess(default_constructor_access);
     addFieldMemberExpr(FD, Ty);
 
-    const auto *RecordDecl = Ty->getAsCXXRecordDecl();
     createSpecialMethodCall(RecordDecl, getInitMethodName(), BodyStmts);
     CXXMethodDecl *FinalizeMethod =
         getMethodByName(RecordDecl, FinalizeMethodName);