Fix bug in MetadataMethod.GetAttributes and add tests for PreserveSig in DllImportAttribute and PreserveSigAttribute.

ICSharpCode.Decompiler.Tests/TypeSystem/TypeSystemLoaderTests.cs

@@ -22,12 +22,10 @@ using System.Collections.Immutable;
 using System.IO;
 using System.Linq;
 using System.Reflection.Metadata;
-using System.Reflection.PortableExecutable;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
 using ICSharpCode.Decompiler.Metadata;
-using ICSharpCode.Decompiler.Semantics;
 using ICSharpCode.Decompiler.TypeSystem;
 using ICSharpCode.Decompiler.TypeSystem.Implementation;
 using NUnit.Framework;
@@ -677,6 +675,26 @@ namespace ICSharpCode.Decompiler.Tests.TypeSystem
 			Assert.AreEqual((int)CharSet.Unicode, dllImport.NamedArguments.Single().Value);
 		}
 
+		[Test]
+		public void DllImportAttributeWithPreserveSigFalse()
+		{
+			IMethod method = GetTypeDefinition(typeof(NonCustomAttributes)).Methods.Single(m => m.Name == "DoNotPreserveSig");
+			IAttribute dllImport = method.GetAttributes().Single();
+			Assert.AreEqual("System.Runtime.InteropServices.DllImportAttribute", dllImport.AttributeType.FullName);
+			Assert.AreEqual("unmanaged.dll", dllImport.FixedArguments[0].Value);
+			Assert.AreEqual(false, dllImport.NamedArguments.Single().Value);
+		}
+
+		[Test]
+		public void PreserveSigAttribute()
+		{
+			IMethod method = GetTypeDefinition(typeof(NonCustomAttributes)).Methods.Single(m => m.Name == "PreserveSigAsAttribute");
+			IAttribute preserveSig = method.GetAttributes().Single();
+			Assert.AreEqual("System.Runtime.InteropServices.PreserveSigAttribute", preserveSig.AttributeType.FullName);
+			Assert.IsTrue(preserveSig.FixedArguments.Length == 0);
+			Assert.IsTrue(preserveSig.NamedArguments.Length == 0);
+		}
+
 		[Test]
 		public void InOutParametersOnRefMethod()
 		{

ICSharpCode.Decompiler.Tests/TypeSystem/TypeSystemTestCase.cs

@@ -153,6 +153,14 @@ namespace ICSharpCode.Decompiler.Tests.TypeSystem
 		[DllImport("unmanaged.dll", CharSet = CharSet.Unicode)]
 		[return: MarshalAs(UnmanagedType.Bool)]
 		public static extern bool DllMethod([In, Out] ref int p);
+
+		[DllImport("unmanaged.dll", PreserveSig = false)]
+		public static extern bool DoNotPreserveSig();
+
+		[PreserveSig]
+		public static void PreserveSigAsAttribute()
+		{
+		}
 	}
 
 	[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode, Pack = 8)]

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataMethod.cs

@@ -332,7 +332,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				if ((implAttributes & MethodImplAttributes.PreserveSig) == MethodImplAttributes.PreserveSig) {
 					implAttributes &= ~MethodImplAttributes.PreserveSig;
 				} else {
-					dllImport.AddNamedArg("PreserveSig", KnownTypeCode.Boolean, true);
+					dllImport.AddNamedArg("PreserveSig", KnownTypeCode.Boolean, false);
 				}
 
 				if ((info.Attributes & MethodImportAttributes.SetLastError) == MethodImportAttributes.SetLastError)