ConditionDetection: Remove empty else-branches.

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -271,6 +271,7 @@
     <Compile Include="DotNetCore\DotNetCorePathFinder.cs" />
     <Compile Include="DotNetCore\DotNetCorePathFinderExtensions.cs" />
     <Compile Include="DotNetCore\UnresolvedAssemblyNameReference.cs" />
+    <Compile Include="IL\Instructions\ILInstructionExtensions.cs" />
     <Compile Include="IL\Transforms\EarlyExpressionTransforms.cs" />
     <Compile Include="IL\Transforms\UsingTransform.cs" />
     <Compile Include="IL\ControlFlow\AsyncAwaitDecompiler.cs" />

ICSharpCode.Decompiler/IL/ControlFlow/ConditionDetection.cs

@@ -176,10 +176,19 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				if (DetectExitPoints.CompatibleExitInstruction(trueExitInst, falseExitInst)) {
 					// if (...) { ...; goto exitPoint; } goto nextBlock; nextBlock: ...; goto exitPoint;
 					// -> if (...) { ... } else { ... } goto exitPoint;
-					context.Step("Inline block as else-branch", ifInst);
-					targetBlock.Instructions.RemoveAt(targetBlock.Instructions.Count - 1);
-					targetBlock.Remove();
-					ifInst.FalseInst = targetBlock;
+					
+					// the else block is not empty or nop-only:
+					if (!targetBlock.IsNopBlock(ignoreExitPoint: falseExitInst)) {
+						context.Step("Inline block as else-branch", ifInst);
+						targetBlock.Instructions.RemoveAt(targetBlock.Instructions.Count - 1);
+						targetBlock.Remove();
+						ifInst.FalseInst = targetBlock;
+					} else {
+						// the else block is empty or nop-only and can be safely removed:
+						context.Step("Remove empty else-branch", ifInst);
+						targetBlock.Instructions.RemoveAt(targetBlock.Instructions.Count - 1);
+						targetBlock.Remove();
+					}
 					exitInst = block.Instructions[block.Instructions.Count - 1] = falseExitInst;
 					Block trueBlock = ifInst.TrueInst as Block;
 					if (trueBlock != null) {

ICSharpCode.Decompiler/IL/Instructions/ILInstructionExtensions.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Linq;
+using System.Collections.Generic;
+using System.Text;
+
+namespace ICSharpCode.Decompiler.IL
+{
+	public static class ILInstructionExtensions
+	{
+		/// <summary>
+		/// Determines whether a block only consists of nop instructions or is empty.
+		/// </summary>
+		public static bool IsNopBlock(this Block block, ILInstruction ignoreExitPoint = null)
+		{
+			if (block == null)
+				throw new ArgumentNullException(nameof(block));
+			return block.Children.Count(i => !(i is Nop) && i != ignoreExitPoint) == 0;
+		}
+	}
+}