static constructors throw NRE if having struct fields and invoked via TypeInitializer

[ufcpp]

The following code throws NullReferenceException on .NET Core (doesn't throw on .NET Framework).
It this a bug?

using System;

struct S { }

class A
{
 static TimeSpan x = default; // throws NRE
 // FYI, generated il is: ldsflda, initobj
}

class B
{
 static S x = default; // throws NRE
}

class C
{
 static S x;
 static C() => x = default; // throws NRE
}

class D
{
 // no exception if static fiealds are primitives or reference types
 // generated il is: ldnull/ldc.i4, stsfld
 static string x = null;
 static int y = 0;
}

static class Program
{
 static void Main()
 {
 Console.WriteLine("----");
 try { typeof(A).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("A"); } // A
 try { typeof(B).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("B"); } // B
 try { typeof(C).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("C"); } // C
 try { typeof(D).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("D"); } // (no excpetion)

 Console.WriteLine("----");
 A a = new A();
 B b = new B();
 C c = new C();
 try { typeof(A).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("A"); } // A
 try { typeof(B).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("B"); } // B
 try { typeof(C).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("C"); } // (no excpetion)
 try { typeof(D).TypeInitializer.Invoke(null, null); } catch { Console.WriteLine("D"); } // (no excpetion)
 }
}

[jkotas]

Yes, this looks like a bug.

[jkotas]

We are missing allocation of boxed statics on this path (look for HasBoxedRegularStatics).