Trimming with TrimMode=full was removing default constructors used by Activator.CreateInstance in variance tests, causing test failures in src/tests/Loader/classloader/generics/Variance/IL.

Changes

• Added [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] to the U type parameter in the following methods across 6 test files (Unbox001-006.cs):
  • UnboxUToTInternal<T,U>()
  • CaseClassUToTWrapper<T,U>()
  • UnboxUToT<T,U>()
• Added required using System.Diagnostics.CodeAnalysis; directive
• The attribute is propagated transitively through all generic callsites in the call chain

// Before
private static void UnboxUToTInternal<T,U>()
{
    T t = (T) Activator.CreateInstance(typeof(U));
}

private static void CaseClassUToTWrapper<T,U>()
{
    UnboxUToTInternal<T,U>();
}

public static bool UnboxUToT<T,U>(bool expected)
{
    CaseClassUToTWrapper<T,U>();
    ...
}

// After
private static void UnboxUToTInternal<T, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] U>()
{
    T t = (T) Activator.CreateInstance(typeof(U));
}

private static void CaseClassUToTWrapper<T, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] U>()
{
    UnboxUToTInternal<T,U>();
}

public static bool UnboxUToT<T, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] U>(bool expected)
{
    CaseClassUToTWrapper<T,U>();
    ...
}

This preserves the parameterless constructors required by the generic variance tests when building with trimming enabled by ensuring the attribute is present at every level of the generic method call chain.

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