Change rules for VisitUnboxAny & fix issue https://github.com/icsharpcode/ILSpy/issues/1256

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

@@ -70,9 +70,11 @@
     <Compile Include="DataFlowTest.cs" />
     <Compile Include="TestCases\Correctness\LocalFunctions.cs" />
     <Compile Include="TestCases\Correctness\RefLocalsAndReturns.cs" />
+    <Compile Include="TestCases\ILPretty\Issue1256.cs" />
     <Compile Include="TestCases\Pretty\OptionalArguments.cs" />
     <Compile Include="TestCases\Pretty\CustomShortCircuitOperators.cs" />
     <Compile Include="TestCases\Pretty\TypeTests.cs" />
+    <None Include="TestCases\ILPretty\Issue1256.il" />
     <None Include="TestCases\Ugly\NoDecimalConstants.Expected.cs" />
     <Compile Include="TestCases\Ugly\NoDecimalConstants.cs" />
     <None Include="TestCases\Disassembler\Pretty\SecurityDeclarations.il" />

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -118,6 +118,12 @@ namespace ICSharpCode.Decompiler.Tests
 			Run();
 		}
 
+		[Test]
+		public void Issue1256()
+		{
+			Run();
+		}
+
 		[Test]
 		public void FSharpLoops_Debug()
 		{

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue1256.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.ILPretty
+{
+	internal class Issue1256
+	{
+		public void Method(Enum e, object o, string s)
+		{
+			int num = (int)(object)e;
+			object obj = new object();
+			int num2 = (int)obj;
+			long num3 = (long)o;
+			int num4 = (int)(object)s;
+			int num5 = (int)num3;
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue1256.il

@@ -0,0 +1,58 @@
+.class private auto ansi beforefieldinit ICSharpCode.Decompiler.Tests.TestCases.ILPretty.Issue1256
+	extends [mscorlib]System.Object
+{
+	// Methods
+	.method public hidebysig 
+		instance void Method (
+			class [mscorlib]System.Enum e,
+			object o,
+			string s
+		) cil managed 
+	{
+		// Method begins at RVA 0x2050
+		// Code size 41 (0x29)
+		.maxstack 1
+		.locals init (
+			[0] int32,
+			[1] object,
+			[2] int32,
+			[3] int64,
+			[4] int32,
+			[5] int32
+		)
+
+		IL_0000: nop
+		IL_0001: ldarg.1
+		IL_0002: unbox.any [mscorlib]System.Int32
+		IL_0007: stloc.0
+		IL_0008: newobj instance void [mscorlib]System.Object::.ctor()
+		IL_000d: stloc.1
+		IL_000e: ldloc.1
+		IL_000f: unbox.any [mscorlib]System.Int32
+		IL_0014: stloc.2
+		IL_0015: ldarg.2
+		IL_0016: unbox.any [mscorlib]System.Int64
+		IL_001b: stloc.3
+		IL_001c: ldarg.3
+		IL_001d: unbox.any [mscorlib]System.Int32
+		IL_0022: stloc.s 4
+		IL_0024: ldloc.3
+		IL_0025: conv.i4
+		IL_0026: stloc.s 5
+		IL_0028: ret
+	} // end of method Issue1256::Method
+
+	.method public hidebysig specialname rtspecialname 
+		instance void .ctor () cil managed 
+	{
+		// Method begins at RVA 0x2085
+		// Code size 8 (0x8)
+		.maxstack 8
+
+		IL_0000: ldarg.0
+		IL_0001: call instance void [mscorlib]System.Object::.ctor()
+		IL_0006: nop
+		IL_0007: ret
+	} // end of method Issue1256::.ctor
+
+} // end of class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.Issue1256

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -1877,10 +1877,6 @@ namespace ICSharpCode.Decompiler.CSharp
 				// isinst followed by unbox.any of the same type is used for as-casts to generic types
 				return arg.WithILInstruction(inst);
 			}
-			if (arg.Type.IsReferenceType != true) {
-				// ensure we treat the input as a reference type
-				arg = arg.ConvertTo(compilation.FindType(KnownTypeCode.Object), this);
-			}
 
 			IType targetType = inst.Type;
 			if (targetType.Kind == TypeKind.TypeParameter) {
@@ -1892,6 +1888,11 @@ namespace ICSharpCode.Decompiler.CSharp
 					arg = arg.ConvertTo(((ITypeParameter)targetType).EffectiveBaseClass, this);
 				}
 			}
+			else {
+				// Before unboxing arg must be a object
+				arg = arg.ConvertTo(compilation.FindType(KnownTypeCode.Object), this);
+			}
+
 			return new CastExpression(ConvertType(targetType), arg.Expression)
 				.WithILInstruction(inst)
 				.WithRR(new ConversionResolveResult(targetType, arg.ResolveResult, Conversion.UnboxingConversion));