Add test cases

ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -167,6 +167,7 @@
     <Compile Include="TestCases\Pretty\Issue3610.cs" />
     <Compile Include="TestCases\Pretty\Issue3611.cs" />
     <Compile Include="TestCases\Pretty\Issue3598.cs" />
+    <Compile Include="Metadata\SignatureBlobComparerTests.cs" />
     <None Include="TestCases\Pretty\Issue3684.dep.cs" />
     <None Include="TestCases\Pretty\Issue3684.cs" />
     <None Include="TestCases\Ugly\NoLocalFunctions.Expected.cs" />

ICSharpCode.Decompiler.Tests/Metadata/SignatureBlobComparerTests.cs

@@ -0,0 +1,365 @@
+// Copyright (c) 2026 Siegfried Pammer
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection.Metadata;
+
+using ICSharpCode.Decompiler.Metadata;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.Decompiler.Tests.Metadata
+{
+	[TestFixture]
+	public class SignatureBlobComparerTests
+	{
+		static MetadataReader Metadata => TypeSystem.TypeSystemLoaderTests.TestAssembly.Metadata;
+
+		#region Helper methods
+
+		/// <summary>
+		/// Finds all MethodDefinitionHandles for methods with the given name in the given type.
+		/// </summary>
+		static List<MethodDefinitionHandle> FindMethods(string typeName, string methodName)
+		{
+			var results = new List<MethodDefinitionHandle>();
+			foreach (var typeHandle in Metadata.TypeDefinitions)
+			{
+				var typeDef = Metadata.GetTypeDefinition(typeHandle);
+				if (!Metadata.StringComparer.Equals(typeDef.Name, typeName))
+					continue;
+
+				foreach (var methodHandle in typeDef.GetMethods())
+				{
+					var methodDef = Metadata.GetMethodDefinition(methodHandle);
+					if (Metadata.StringComparer.Equals(methodDef.Name, methodName))
+						results.Add(methodHandle);
+				}
+			}
+			return results;
+		}
+
+		/// <summary>
+		/// Finds a single MethodDefinitionHandle for a method with the given name in the given type.
+		/// </summary>
+		static MethodDefinitionHandle FindMethod(string typeName, string methodName)
+		{
+			var results = FindMethods(typeName, methodName);
+			Assert.That(results.Count, Is.EqualTo(1),
+				$"Expected exactly one method '{methodName}' in '{typeName}', found {results.Count}");
+			return results[0];
+		}
+
+		/// <summary>
+		/// Finds a MethodDefinitionHandle matching on name and parameter count.
+		/// </summary>
+		static MethodDefinitionHandle FindMethod(string typeName, string methodName, int parameterCount)
+		{
+			var results = FindMethods(typeName, methodName);
+			var filtered = results.Where(h => {
+				var m = Metadata.GetMethodDefinition(h);
+				return m.GetParameters().Count == parameterCount;
+			}).ToList();
+			Assert.That(filtered.Count, Is.EqualTo(1),
+				$"Expected exactly one method '{methodName}' with {parameterCount} params in '{typeName}', found {filtered.Count}");
+			return filtered[0];
+		}
+
+		static BlobReader GetSignatureBlob(MethodDefinitionHandle handle)
+		{
+			var method = Metadata.GetMethodDefinition(handle);
+			return Metadata.GetBlobReader(method.Signature);
+		}
+
+		static bool CompareSignatures(MethodDefinitionHandle a, MethodDefinitionHandle b)
+		{
+			return SignatureBlobComparer.EqualsMethodSignature(
+				GetSignatureBlob(a), GetSignatureBlob(b),
+				Metadata, Metadata);
+		}
+
+		#endregion
+
+		#region Identity / reflexive tests
+
+		[Test]
+		public void SameMethod_IsEqual()
+		{
+			// SimplePublicClass.Method() compared to itself
+			var method = FindMethod("SimplePublicClass", "Method");
+			Assert.That(CompareSignatures(method, method), Is.True);
+		}
+
+		[Test]
+		public void Constructor_ComparedToItself_IsEqual()
+		{
+			var ctor = FindMethod("SimplePublicClass", ".ctor");
+			Assert.That(CompareSignatures(ctor, ctor), Is.True);
+		}
+
+		[Test]
+		public void StaticMethod_ComparedToItself_IsEqual()
+		{
+			// StaticClass.Extension(this object) — it's static at the IL level
+			var method = FindMethod("StaticClass", "Extension");
+			Assert.That(CompareSignatures(method, method), Is.True);
+		}
+
+		#endregion
+
+		#region Same name, different signatures
+
+		[Test]
+		public void DifferentParameterTypes_NotEqual()
+		{
+			// MethodWithOptionalParameter(int) vs MethodWithParamsArray(object[])
+			var intParam = FindMethod("ParameterTests", "MethodWithOptionalParameter");
+			var arrayParam = FindMethod("ParameterTests", "MethodWithParamsArray");
+			Assert.That(CompareSignatures(intParam, arrayParam), Is.False);
+		}
+
+		[Test]
+		public void RefVsOut_SameAtSignatureLevel()
+		{
+			// ref and out are both ELEMENT_TYPE_BYREF at the blob level;
+			// the out modifier is only represented via attributes.
+			var methodRef = FindMethod("ParameterTests", "MethodWithRefParameter");
+			var methodOut = FindMethod("ParameterTests", "MethodWithOutParameter");
+			Assert.That(CompareSignatures(methodRef, methodOut), Is.True);
+		}
+
+		[Test]
+		public void RefVsIn_SameAtSignatureLevel()
+		{
+			// ref and in are both ELEMENT_TYPE_BYREF at the blob level;
+			// the in modifier is only represented via IsReadOnlyAttribute.
+			var methodRef = FindMethod("ParameterTests", "MethodWithRefParameter");
+			var methodIn = FindMethod("ParameterTests", "MethodWithInParameter");
+			Assert.That(CompareSignatures(methodRef, methodIn), Is.True);
+		}
+
+		[Test]
+		public void ByRefVsNonByRef_NotEqual()
+		{
+			// MethodWithRefParameter(ref int) vs MethodWithOptionalParameter(int)
+			// byref int vs plain int should differ at the blob level
+			var byRef = FindMethod("ParameterTests", "MethodWithRefParameter");
+			var plain = FindMethod("ParameterTests", "MethodWithOptionalParameter");
+			Assert.That(CompareSignatures(byRef, plain), Is.False);
+		}
+
+		[Test]
+		public void DifferentParameterCount_NotEqual()
+		{
+			// Compare a method with 0 params to one with 1 param
+			var method0 = FindMethod("SimplePublicClass", "Method"); // 0 params
+			var method1 = FindMethod("ParameterTests", "MethodWithOutParameter"); // 1 param
+			Assert.That(CompareSignatures(method0, method1), Is.False);
+		}
+
+		[Test]
+		public void DifferentReturnType_NotEqual()
+		{
+			// SimplePublicClass.Method() returns void
+			// PropertyTest has a getter that returns string (get_Item)
+			var voidMethod = FindMethod("SimplePublicClass", "Method");
+			var stringGetter = FindMethod("PropertyTest", "get_Item");
+			Assert.That(CompareSignatures(voidMethod, stringGetter), Is.False);
+		}
+
+		#endregion
+
+		#region Generic methods
+
+		[Test]
+		public void GenericMethod_ComparedToItself_IsEqual()
+		{
+			// GenericClass<A,B>.TestMethod<K,V>(string)
+			var method = FindMethod("GenericClass`2", "TestMethod");
+			Assert.That(CompareSignatures(method, method), Is.True);
+		}
+
+		[Test]
+		public void GenericMethod_DifferentArity_NotEqual()
+		{
+			// TestMethod<K,V>(string) has 2 type params
+			// GetIndex<T>(T) has 1 type param
+			var testMethod = FindMethod("GenericClass`2", "TestMethod");
+			var getIndex = FindMethod("GenericClass`2", "GetIndex");
+			Assert.That(CompareSignatures(testMethod, getIndex), Is.False);
+		}
+
+		[Test]
+		public void GenericMethodWithOneTypeParam_ComparedToItself_IsEqual()
+		{
+			var method = FindMethod("GenericClass`2", "GetIndex");
+			Assert.That(CompareSignatures(method, method), Is.True);
+		}
+
+		[Test]
+		public void NonGenericVsGenericMethod_NotEqual()
+		{
+			// SimplePublicClass.Method() — non-generic
+			// GenericClass<A,B>.GetIndex<T>(T) — generic
+			var nonGeneric = FindMethod("SimplePublicClass", "Method");
+			var generic = FindMethod("GenericClass`2", "GetIndex");
+			Assert.That(CompareSignatures(nonGeneric, generic), Is.False);
+		}
+
+		#endregion
+
+		#region Instance vs static
+
+		[Test]
+		public void InstanceVsStatic_DifferentCallingConvention_NotEqual()
+		{
+			// An instance method vs a static method — calling convention differs in the signature header
+			// StaticClass.Extension is static; SimplePublicClass.Method is instance
+			var staticMethod = FindMethod("StaticClass", "Extension");
+			var instanceMethod = FindMethod("SimplePublicClass", "Method");
+			Assert.That(CompareSignatures(staticMethod, instanceMethod), Is.False);
+		}
+
+		#endregion
+
+		#region Methods with same signature across different types
+
+		[Test]
+		public void SameSignatureInDifferentTypes_IsEqual()
+		{
+			// Both SimplePublicClass and ParameterTests have parameterless instance constructors
+			var ctor1 = FindMethod("SimplePublicClass", ".ctor");
+			var ctor2 = FindMethod("ParameterTests", ".ctor");
+			Assert.That(CompareSignatures(ctor1, ctor2), Is.True);
+		}
+
+		#endregion
+
+		#region Methods involving complex types
+
+		[Test]
+		public void MethodWithArrayParam_ComparedToItself_IsEqual()
+		{
+			// ParameterTests.MethodWithParamsArray(params object[])
+			var method = FindMethod("ParameterTests", "MethodWithParamsArray");
+			Assert.That(CompareSignatures(method, method), Is.True);
+		}
+
+		[Test]
+		public void MethodWithOptionalParam_ComparedToNonOptional_IsEqual()
+		{
+			// At the signature blob level, optional vs required doesn't matter —
+			// the signatures are the same if the types match.
+			// MethodWithOptionalParameter(int) vs MethodWithEnumOptionalParameter(StringComparison)
+			// These have different parameter types, so they should NOT be equal.
+			var optionalInt = FindMethod("ParameterTests", "MethodWithOptionalParameter");
+			var optionalEnum = FindMethod("ParameterTests", "MethodWithEnumOptionalParameter");
+			Assert.That(CompareSignatures(optionalInt, optionalEnum), Is.False);
+		}
+
+		[Test]
+		public void VarArgsMethod_ComparedToItself_IsEqual()
+		{
+			var method = FindMethod("ParameterTests", "VarArgsMethod");
+			Assert.That(CompareSignatures(method, method), Is.True);
+		}
+
+		[Test]
+		public void VarArgsMethod_VsNormalMethod_NotEqual()
+		{
+			// VarArgsMethod uses __arglist calling convention
+			var varArgs = FindMethod("ParameterTests", "VarArgsMethod");
+			var normal = FindMethod("SimplePublicClass", "Method");
+			Assert.That(CompareSignatures(varArgs, normal), Is.False);
+		}
+
+		#endregion
+
+		#region Indexer accessors
+
+		[Test]
+		public void IndexerGetter_ComparedToItself_IsEqual()
+		{
+			var getter = FindMethod("PropertyTest", "get_Item");
+			Assert.That(CompareSignatures(getter, getter), Is.True);
+		}
+
+		[Test]
+		public void IndexerGetter_VsSetter_NotEqual()
+		{
+			var getter = FindMethod("PropertyTest", "get_Item");
+			var setter = FindMethod("PropertyTest", "set_Item");
+			Assert.That(CompareSignatures(getter, setter), Is.False);
+		}
+
+		#endregion
+
+		#region DllImport / extern methods
+
+		[Test]
+		public void DllImportMethod_ComparedToItself_IsEqual()
+		{
+			var method = FindMethod("NonCustomAttributes", "DllMethod");
+			Assert.That(CompareSignatures(method, method), Is.True);
+		}
+
+		#endregion
+
+		#region Explicit interface implementation
+
+		[Test]
+		public void ExplicitImpl_VsRegularMethod_SameSignature()
+		{
+			// ExplicitImplementationTests has both M(int) and IExplicitImplementationTests.M(int)
+			// Their signatures should be identical at the blob level
+			var methods = FindMethods("ExplicitImplementationTests", "M");
+			Assert.That(methods.Count, Is.EqualTo(1),
+				"Explicit impl has a mangled name, so only one 'M' should be found");
+		}
+
+		#endregion
+
+		#region Symmetric property
+
+		[Test]
+		public void Comparison_IsSymmetric()
+		{
+			var method1 = FindMethod("SimplePublicClass", "Method");
+			var method2 = FindMethod("ParameterTests", "MethodWithOutParameter");
+
+			bool forward = CompareSignatures(method1, method2);
+			bool backward = CompareSignatures(method2, method1);
+			Assert.That(forward, Is.EqualTo(backward), "Comparison should be symmetric");
+		}
+
+		[Test]
+		public void Comparison_IsSymmetric_WhenEqual()
+		{
+			var ctor1 = FindMethod("SimplePublicClass", ".ctor");
+			var ctor2 = FindMethod("ParameterTests", ".ctor");
+
+			bool forward = CompareSignatures(ctor1, ctor2);
+			bool backward = CompareSignatures(ctor2, ctor1);
+			Assert.That(forward, Is.True);
+			Assert.That(backward, Is.True);
+		}
+
+		#endregion
+	}
+}