int64 UProperty with ExposeOnSpawn meta tag won't compile from a C++ UUserWidget class.
1. Create a new C++ Project in UE 4.24.3
2. Create a new C++ Class based on UUserWidget.
3. Within the header file declare the following
Result: Error: ExposeOnSpawn - Property cannot be exposed
Expected: Successful Compile
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-91150 in the post.