.net 9 analysis

M6502/M6502.Symbols/IdentifiableSection.cs

@@ -1,6 +1,5 @@
 namespace M6502.Symbols
 {
-    using System.Collections;
     using System.Diagnostics;
 
     public class IdentifiableSection : Section

M6502/M6502.Symbols/Section.cs

@@ -23,6 +23,7 @@
 
         protected static ReflectedSectionProperties GetSectionProperties(System.Type type)
         {
+            ArgumentNullException.ThrowIfNull(type);
             var obtained = SectionPropertiesCache.TryGetValue(type, out var properties);
             Debug.Assert(obtained, $"Section properties for {type.Name} have not been built");
             Debug.Assert(properties is not null);

M6502/M6502.Symbols/Symbol.cs

@@ -1,7 +1,5 @@
 namespace M6502.Symbols
 {
-    using System.Collections.Generic;
-
     // sym id = 16, name = "solve", addrsize = absolute, size = 274, scope = 0, def = 94,ref=144+17+351,val=0xF314,seg=6,type=lab
     [Section("symbol", "Symbols")]
     public sealed class Symbol(Parser container) : NamedSection(container)

M6502/M6502.Test/Board.cs

@@ -11,7 +11,7 @@ namespace M6502.Test
     using System.Text;
     using System.Threading.Tasks;
 
-    internal class Board : Bus
+    internal sealed class Board : Bus
     {
         private readonly Configuration configuration;
         private readonly Ram ram = new(0x10000);