Static fields in interfaces should cause the compiler to emit `beforefieldinit` on the interface

[siegfriedpammer]

Version Used:
Microsoft Visual Studio Community 2022
Version 17.6.4
VisualStudio.17.Release/17.6.4+33815.320
Microsoft .NET Framework
Version 4.8.09037

Installed Version: Community

C# Tools 4.6.0-3.23259.8+c3cc1d0ceeab1a65da0217e403851a1e8a30086a
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Steps to Reproduce:

1. the following C# code utilizing static interface members

internal interface I
{
	static int f = 42;
}

is compiled to the following IL (using a simple test project targeting C# 11 and net7.0):

.class interface private auto ansi abstract I
{
	// Fields
	.field public static int32 f

	// Methods
	.method private hidebysig specialname rtspecialname static 
		void .cctor () cil managed 
	{
		.maxstack 8

		IL_0000: ldc.i4.s 42
		IL_0002: stsfld int32 I::f
		IL_0007: ret
	} // end of method I::.cctor

} // end of class I

Expected Behavior:

I would expect the interface to have the beforefieldinit attribute.

Actual Behavior:

The beforefieldinit attribute is missing, this results in unnecessary runtime overhead see also https://godbolt.org/z/jxbxGKrv1

[jcouv]

Yup, it looks like our rule for emitting beforefieldinit is out-of-date. It should be updated now that interfaces can contain fields:

// in NamedTypeSymbolAdapter
        bool Cci.ITypeDefinition.IsBeforeFieldInit
        {
            get
            {
                CheckDefinitionInvariant();

                switch (AdaptedNamedTypeSymbol.TypeKind)
                {
                    case TypeKind.Enum:
                    case TypeKind.Delegate:
                    //C# interfaces don't have fields so the flag doesn't really matter, but Dev10 omits it
                    case TypeKind.Interface:
                        return false;
                }

                //apply the beforefieldinit attribute unless there is an explicitly specified static constructor
                foreach (var member in AdaptedNamedTypeSymbol.GetMembers(WellKnownMemberNames.StaticConstructorName))
                {
                    if (!member.IsImplicitlyDeclared)
                    {
                        return false;
                    }
                }

                return true;
            }
        }