While working on my own array types, I encountered this issue, where one of my unit tests passes for Clang, but fails on MSVC with the following messages:

error C7595: 'UnitTest': call to immediate function is not a constant expression  
note: a non-constant (sub-)expression was encountered  
note: the call stack of the evaluation (the oldest call first) is  
note: while evaluating function 'void UnitTest(void)'  

https://godbolt.org/z/KrbWMe8sM

Removing the std::move from line 54 makes it work correctly in this whittled-down example, but is not acceptable for the full version where I want to distinguish between moving and copying.

Is this a bug with MSVC, or is Clang incorrect in accepting this code?