Fix five small analyzer warnings.

* ExtensionDeclaration.SymbolKind (CA1065) — was throwing
  NotImplementedException; return SymbolKind.TypeDefinition to match
  TypeDeclaration / DelegateDeclaration, since `extension` declarations
  are type-level.
* CustomAttribute.DecodeValue (CA2002) — replace `lock(this)` on the
  sealed-but-internal class with a private syncRoot field.
* PlainTextOutput (CA1001) — implement IDisposable; track an
  ownsWriter flag so we only dispose the underlying TextWriter when
  the parameterless constructor created its own StringWriter.
* DotNetCorePathFinder (CA1060) — move the libc realpath / free
  PInvokes into a private nested NativeMethods class.
* ILSpy.ReadyToRun (CA1016) — add [assembly: AssemblyVersion("1.0.0.0")]
  in Properties/AssemblyInfo.cs to match the BamlDecompiler plugin.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ICSharpCode.Decompiler/CSharp/Syntax/TypeMembers/ExtensionDeclaration.cs

@@ -24,7 +24,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	{
 		public readonly static TokenRole ExtensionKeywordRole = new TokenRole("extension");
 
-		public override SymbolKind SymbolKind => throw new System.NotImplementedException();
+		public override SymbolKind SymbolKind => SymbolKind.TypeDefinition;
 
 		public AstNodeCollection<TypeParameterDeclaration> TypeParameters {
 			get { return GetChildrenByRole(Roles.TypeParameter); }

ICSharpCode.Decompiler/Metadata/DotNetCorePathFinder.cs

@@ -318,7 +318,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			fixed (byte* input = bytes)
 			{
 
-				byte* output = GetRealPath(input, null);
+				byte* output = NativeMethods.GetRealPath(input, null);
 				if (output == null)
 				{
 					return null;
@@ -330,15 +330,18 @@ namespace ICSharpCode.Decompiler.Metadata
 				}
 				byte[] result = new byte[len];
 				Marshal.Copy((IntPtr)output, result, 0, result.Length);
-				Free(output);
+				NativeMethods.Free(output);
 				return encoding.GetString(result);
 			}
 		}
 
-		[DllImport("libc", EntryPoint = "realpath")]
-		static extern unsafe byte* GetRealPath(byte* path, byte* resolvedPath);
+		static class NativeMethods
+		{
+			[DllImport("libc", EntryPoint = "realpath")]
+			internal static extern unsafe byte* GetRealPath(byte* path, byte* resolvedPath);
 
-		[DllImport("libc", EntryPoint = "free")]
-		static extern unsafe void Free(void* ptr);
+			[DllImport("libc", EntryPoint = "free")]
+			internal static extern unsafe void Free(void* ptr);
+		}
 	}
 }

ICSharpCode.Decompiler/Output/PlainTextOutput.cs

@@ -28,9 +28,10 @@ using ICSharpCode.Decompiler.TypeSystem;
 
 namespace ICSharpCode.Decompiler
 {
-	public sealed class PlainTextOutput : ITextOutput
+	public sealed class PlainTextOutput : ITextOutput, IDisposable
 	{
 		readonly TextWriter writer;
+		readonly bool ownsWriter;
 		int indent;
 		bool needsIndent;
 
@@ -44,11 +45,19 @@ namespace ICSharpCode.Decompiler
 			if (writer == null)
 				throw new ArgumentNullException(nameof(writer));
 			this.writer = writer;
+			this.ownsWriter = false;
 		}
 
 		public PlainTextOutput()
 		{
 			this.writer = new StringWriter();
+			this.ownsWriter = true;
+		}
+
+		public void Dispose()
+		{
+			if (ownsWriter)
+				writer.Dispose();
 		}
 
 		public TextLocation Location {

ICSharpCode.Decompiler/TypeSystem/Implementation/CustomAttribute.cs

@@ -40,6 +40,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		CustomAttributeValue<IType> value;
 		bool valueDecoded;
 		bool hasDecodeErrors;
+		readonly object syncRoot = new object();
 
 		internal CustomAttribute(MetadataModule module, IMethod attrCtor, CustomAttributeHandle handle)
 		{
@@ -76,7 +77,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 
 		void DecodeValue()
 		{
-			lock (this)
+			lock (syncRoot)
 			{
 				try
 				{

ILSpy.ReadyToRun/Properties/AssemblyInfo.cs

@@ -8,7 +8,8 @@ using System.Runtime.Versioning;
 [assembly: TargetPlatform("Windows10.0")]
 [assembly: SupportedOSPlatform("Windows7.0")]
 
-// General Information about an assembly is controlled through the following 
+// General Information about an assembly is controlled through the following
 // set of attributes. Change these attribute values to modify the information
 // associated with an assembly.
 [assembly: NeutralResourcesLanguage("en-US")]
+[assembly: AssemblyVersion("1.0.0.0")]