Draft PR to get FB (#24)

* Draft PR to get FB

* Still not refactored and in draft but incorporate Sven's FB

* Partial support for Local var signature

* FB

Author: LakshanF

src/coreclr/tools/ILTrim/ILTrim/DependencyAnalysis/EcmaSignatureParser.cs

@@ -0,0 +1,70 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Reflection.Metadata.Ecma335;
+
+using System.Reflection.Metadata;
+
+namespace ILTrim.DependencyAnalysis
+{
+    public struct EcmaSignatureParser
+    {
+        private MetadataReader _reader;
+        private BlobBuilder _builder;
+        private TokenMap _tokenMap;
+
+        public EcmaSignatureParser(MetadataReader reader, TokenMap tokenMap)
+        {
+            _reader = reader;
+            _builder = new BlobBuilder();
+            _tokenMap = tokenMap;
+        }
+
+        public byte[] GetLocalVariableBlob(StandaloneSignatureHandle handle)
+        {
+            StandaloneSignature standaloneSig = _reader.GetStandaloneSignature(handle);
+            BlobReader signatureReader = _reader.GetBlobReader(standaloneSig.Signature);
+            SignatureHeader header = signatureReader.ReadSignatureHeader();
+            int varCount = signatureReader.ReadCompressedInteger();
+            var blobBuilder = new BlobBuilder();
+            var encoder = new BlobEncoder(blobBuilder);
+            var localEncoder = encoder.LocalVariableSignature(varCount);
+
+            for (int i = 0; i < varCount; i++)
+            {
+                SignatureTypeCode typeCode = signatureReader.ReadSignatureTypeCode();
+                switch (typeCode)
+                {
+                    case SignatureTypeCode.TypeHandle:
+                        {
+                            var localVarTypeEncoder = localEncoder.AddVariable();
+
+                            var signatureTypeEncoder = localVarTypeEncoder.Type();
+                            signatureTypeEncoder.Type(_tokenMap.MapToken((TypeDefinitionHandle)signatureReader.ReadTypeHandle()), isValueType: false);
+                            break;
+                        }
+
+                    case SignatureTypeCode.Int32:
+                        {
+                            var localVarTypeEncoder = localEncoder.AddVariable();
+
+                            var signatureTypeEncoder = localVarTypeEncoder.Type();
+                            signatureTypeEncoder.Int32();
+                            break;
+                        }
+
+                    default:
+                        break;
+                }
+            }
+
+            return blobBuilder.ToArray();
+        }
+
+    }
+}

src/coreclr/tools/ILTrim/ILTrim/DependencyAnalysis/TokenBased/StandaloneSignatureNode.cs

@@ -3,6 +3,10 @@
 
 using System.Collections.Generic;
 using System.Reflection.Metadata;
+using System.Reflection.Metadata.Ecma335;
+using System.Linq;
+
+using Internal.TypeSystem;
 
 namespace ILTrim.DependencyAnalysis
 {
@@ -20,20 +24,44 @@ public StandaloneSignatureNode(EcmaModule module, StandaloneSignatureHandle hand
 
         public override IEnumerable<DependencyListEntry> GetStaticDependencies(NodeFactory factory)
         {
-            // TODO: the signature might depend on other tokens
+            // @TODO: These need to go EcmaSignatureParser
+            // Cannot think of a design that can move this logic to that struct
+
+            MetadataReader reader = _module.MetadataReader;
+
+            StandaloneSignature standaloneSig = reader.GetStandaloneSignature(Handle);
+
+            BlobReader signatureReader = reader.GetBlobReader(standaloneSig.Signature);
+
+            if (signatureReader.ReadSignatureHeader().Kind != SignatureKind.LocalVariables)
+                ThrowHelper.ThrowInvalidProgramException();
+
+            int count = signatureReader.ReadCompressedInteger();
+
+            for (int i = 0; i < count; i++)
+            {
+                SignatureTypeCode typeCode = signatureReader.ReadSignatureTypeCode();
+                switch (typeCode)
+                {
+                    case SignatureTypeCode.TypeHandle:
+                        TypeDefinitionHandle typeDefHandle = (TypeDefinitionHandle)signatureReader.ReadTypeHandle();
+                        yield return new DependencyListEntry(factory.TypeDefinition(_module, typeDefHandle), "Local variable type");
+                        break;
+                }
+            }
+
             yield break;
         }
 
         protected override EntityHandle WriteInternal(ModuleWritingContext writeContext)
         {
-            MetadataReader reader = _module.MetadataReader;
-            StandaloneSignature standaloneSig = reader.GetStandaloneSignature(Handle);
+            EcmaSignatureParser signatureParser = new EcmaSignatureParser(_module.MetadataReader, writeContext.TokenMap);
+            byte[] blobBytes = signatureParser.GetLocalVariableBlob(Handle);
 
-            // TODO: the signature might have tokens we need to rewrite
             var builder = writeContext.MetadataBuilder;
             return builder.AddStandaloneSignature(
-                builder.GetOrAddBlob(reader.GetBlobBytes(standaloneSig.Signature))
-                );
+                builder.GetOrAddBlob(blobBytes));
+
         }
 
         public override string ToString()

src/coreclr/tools/ILTrim/repro/Program.cs

@@ -13,6 +13,9 @@ interface IProgram
     static int FirstMethod() => 300;
     static int Main()
     {
+#pragma warning disable 0219
+        IAnotherType mylocal = default;
+#pragma warning restore 0219
         return 42;
     }
     static void LastMethod(int someParameter) { }