Fix #1682, fix #1949, fix #2394 and fix #3684: Added basic algorithm of IsAccessorInterfaceImplementationRuntimeHelper

Author: siegfriedpammer

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3684.cs

@@ -8,6 +8,7 @@ public static class CrossAssemblyProperties
 		public interface IInterface
 		{
 			string Name { get; set; }
+			T Convert<T>(T input);
 		}
 
 		public class DerivedClass : BaseClass, IInterface

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Issue3684.dep.cs

@@ -12,5 +12,7 @@ public string Name {
 				name = value;
 			}
 		}
+
+		public T Convert<T>(T input) { return input; }
 	}
 }

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -292,6 +292,8 @@ public static bool MemberIsHidden(MetadataFile module, EntityHandle member, Deco
 					name = metadata.GetString(method.Name);
 					if (name == ".ctor" && method.RelativeVirtualAddress == 0 && metadata.GetTypeDefinition(method.GetDeclaringType()).Attributes.HasFlag(System.Reflection.TypeAttributes.Import))
 						return true;
+					if (module is PEFile m && IsAccessorInterfaceImplementationRuntimeHelper(m, methodHandle))
+						return true;
 					if (settings.LocalFunctions && LocalFunctionDecompiler.IsLocalFunctionMethod(module, methodHandle))
 						return true;
 					if (settings.AnonymousMethods && methodHandle.HasGeneratedName(metadata) && methodHandle.IsCompilerGenerated(metadata))
@@ -386,6 +388,163 @@ static bool IsPrimaryConstructorParameterBackingField(SRM.FieldDefinition field,
 			return name.StartsWith("<", StringComparison.Ordinal) && name.EndsWith(">P", StringComparison.Ordinal);
 		}
 
+		static bool IsAccessorInterfaceImplementationRuntimeHelper(PEFile module, MethodDefinitionHandle handle)
+		{
+			var metadata = module.Metadata;
+			var method = metadata.GetMethodDefinition(handle);
+			if ((method.Attributes & System.Reflection.MethodAttributes.Static) != 0)
+				return false;
+			string rawName = metadata.GetString(method.Name);
+			int dot = rawName.LastIndexOf('.');
+			if (dot < 0)
+				return false;
+			string name = rawName.Substring(dot + 1);
+			if (handle.GetMethodImplementations(metadata).Length == 0)
+				return false;
+			if (method.RelativeVirtualAddress == 0)
+				return false;
+			if (!name.StartsWith("get_", StringComparison.Ordinal) &&
+				!name.StartsWith("set_", StringComparison.Ordinal) &&
+				!name.StartsWith("add_", StringComparison.Ordinal) &&
+				!name.StartsWith("remove_", StringComparison.Ordinal) &&
+				!name.StartsWith("raise_", StringComparison.Ordinal))
+			{
+				return false;
+			}
+
+			var signature = metadata.GetBlobReader(method.Signature);
+			(int genericParameterCount, int parameterCount) = SignatureBlobComparer.ReadParameterCount(ref signature);
+			if (genericParameterCount == -1 || parameterCount == -1)
+				return false;
+			signature.Reset();
+
+			int maximumMethodSize = 4 * (parameterCount + 1) + 5 + 1;
+
+			var body = module.Reader.GetMethodBody(method.RelativeVirtualAddress);
+			var reader = body.GetILReader();
+
+			if (reader.RemainingBytes > maximumMethodSize)
+				return false;
+
+			for (int i = 0; i < parameterCount + 1; i++)
+			{
+				int index;
+				switch (reader.DecodeOpCode())
+				{
+					case ILOpCode.Ldarg:
+						index = reader.ReadUInt16();
+						if (index != i)
+							return false;
+						break;
+					case ILOpCode.Ldarg_s:
+						index = reader.ReadByte();
+						if (index != i)
+							return false;
+						break;
+					case ILOpCode.Ldarg_0:
+						if (i != 0)
+							return false;
+						break;
+					case ILOpCode.Ldarg_1:
+						if (i != 1)
+							return false;
+						break;
+					case ILOpCode.Ldarg_2:
+						if (i != 2)
+							return false;
+						break;
+					case ILOpCode.Ldarg_3:
+						if (i != 3)
+							return false;
+						break;
+					default:
+						return false;
+				}
+			}
+
+			if (reader.DecodeOpCode() != ILOpCode.Call)
+				return false;
+
+			EntityHandle targetHandle = MetadataTokenHelpers.EntityHandleOrNil(reader.ReadInt32());
+			if (targetHandle.IsNil)
+				return false;
+
+			if (reader.DecodeOpCode() != ILOpCode.Ret)
+				return false;
+
+			if (reader.RemainingBytes != 0)
+				return false;
+
+			BlobReader signature2;
+			string otherName;
+
+			switch (targetHandle.Kind)
+			{
+				case HandleKind.MethodDefinition:
+					if (genericParameterCount != 0)
+						return false;
+					var methodDef = metadata.GetMethodDefinition((MethodDefinitionHandle)targetHandle);
+					signature2 = metadata.GetBlobReader(methodDef.Signature);
+					otherName = metadata.GetString(methodDef.Name);
+					break;
+				case HandleKind.MethodSpecification:
+					if (genericParameterCount == 0)
+						return false;
+					var methodSpec = metadata.GetMethodSpecification((MethodSpecificationHandle)targetHandle);
+					var instantiationBlob = metadata.GetBlobReader(methodSpec.Signature);
+					if (!IsIdentityInstantiation(ref instantiationBlob, genericParameterCount))
+						return false;
+					switch (methodSpec.Method.Kind)
+					{
+						case HandleKind.MethodDefinition:
+							var methodSpecDef = metadata.GetMethodDefinition((MethodDefinitionHandle)methodSpec.Method);
+							signature2 = metadata.GetBlobReader(methodSpecDef.Signature);
+							otherName = metadata.GetString(methodSpecDef.Name);
+							break;
+						case HandleKind.MemberReference:
+							var methodSpecRef = metadata.GetMemberReference((MemberReferenceHandle)methodSpec.Method);
+							if (methodSpecRef.GetKind() != MemberReferenceKind.Method)
+								return false;
+							signature2 = metadata.GetBlobReader(methodSpecRef.Signature);
+							otherName = metadata.GetString(methodSpecRef.Name);
+							break;
+						default:
+							return false;
+					}
+					break;
+				case HandleKind.MemberReference:
+					var methodRef = metadata.GetMemberReference((MemberReferenceHandle)targetHandle);
+					if (methodRef.GetKind() != MemberReferenceKind.Method)
+						return false;
+					signature2 = metadata.GetBlobReader(methodRef.Signature);
+					otherName = metadata.GetString(methodRef.Name);
+					break;
+				default:
+					return false;
+			}
+
+			if (otherName != name)
+				return false;
+			return SignatureBlobComparer.EqualsMethodSignature(signature, signature2, metadata, metadata, skipModifiers: true);
+
+			static bool IsIdentityInstantiation(ref BlobReader reader, int expectedCount)
+			{
+				// Format: GENRICINST count type1 type2 ...
+				if (reader.ReadByte() != 0x0A) // GENERICINST
+					return false;
+				if (!reader.TryReadCompressedInteger(out int count) || count != expectedCount)
+					return false;
+				for (int i = 0; i < count; i++)
+				{
+					if (reader.ReadByte() != 0x1E) // ELEMENT_TYPE_MVAR
+						return false;
+					if (!reader.TryReadCompressedInteger(out int index) || index != i)
+						return false;
+				}
+				return true;
+			}
+		}
+
 		static bool IsSwitchOnStringCache(SRM.FieldDefinition field, MetadataReader metadata)
 		{
 			return metadata.GetString(field.Name).StartsWith("<>f__switch", StringComparison.Ordinal);