Inheritance: SimpleValHLSL
 public void DeclareAndInitLocalImpl(
     SimpleValHLSL local,
     LitHLSL init,
     Span span)
 {
     span.WriteLine("{0} = {1};",
         local.RealType.DeclareVar(local.Name),
         init);
 }
 public void BindAttrLit(
     MidAttributeWrapperDecl attr,
     string lit)
 {
     var type = EmitType(attr.Type);
     if (!(type is RealTypeHLSL))
     {
         throw new NotImplementedException();
     }
     var val = new LitHLSL((RealTypeHLSL)type, lit);
     BindAttr(attr, val);
 }