Generate switch default case. Closes #26

ICSharpCode.Decompiler/Ast/AstMethodBodyBuilder.cs

@@ -123,7 +123,11 @@ namespace ICSharpCode.Decompiler.Ast
 				SwitchStatement switchStmt = new SwitchStatement() { Expression = (Expression)TransformExpression(ilSwitch.Condition) };
 				foreach (var caseBlock in ilSwitch.CaseBlocks) {
 					SwitchSection section = new SwitchSection();
-					section.CaseLabels.AddRange(caseBlock.Values.Select(i => new CaseLabel() { Expression = AstBuilder.MakePrimitive(i, ilSwitch.Condition.InferredType) }));
+					if (caseBlock.Values != null) {
+						section.CaseLabels.AddRange(caseBlock.Values.Select(i => new CaseLabel() { Expression = AstBuilder.MakePrimitive(i, ilSwitch.Condition.InferredType) }));
+					} else {
+						section.CaseLabels.Add(new CaseLabel());
+					}
 					section.Statements.Add(TransformBlock(caseBlock));
 					switchStmt.SwitchSections.Add(section);
 				}

ICSharpCode.Decompiler/ILAst/GotoRemoval.cs

@@ -60,6 +60,8 @@ namespace ICSharpCode.Decompiler.ILAst
 			// Remove redundant case blocks altogether
 			foreach(ILSwitch ilSwitch in method.GetSelfAndChildrenRecursive<ILSwitch>()) {
 				foreach(ILBlock ilCase in ilSwitch.CaseBlocks) {
+					Debug.Assert(ilCase.EntryGoto == null);
+					
 					int count = ilCase.Body.Count;
 					if (count >= 2) {
 						if (!ilCase.Body[count - 2].CanFallthough() &&
@@ -68,7 +70,12 @@ namespace ICSharpCode.Decompiler.ILAst
 						}
 					}
 				}
-				ilSwitch.CaseBlocks.RemoveAll(b => b.Body.Count == 1 && b.Body.Single().Match(ILCode.LoopOrSwitchBreak));
+				
+				var defaultCase = ilSwitch.CaseBlocks.Where(cb => cb.Values == null).SingleOrDefault();
+				// If there is no default block, remove empty case blocks
+				if (defaultCase == null || (defaultCase.Body.Count == 1 && defaultCase.Body.Single().Match(ILCode.LoopOrSwitchBreak))) {
+					ilSwitch.CaseBlocks.RemoveAll(b => b.Body.Count == 1 && b.Body.Single().Match(ILCode.LoopOrSwitchBreak));
+				}
 			}
 			
 			// Remove redundant return

ICSharpCode.Decompiler/ILAst/ILAstOptimizer.cs

@@ -584,18 +584,20 @@ namespace ICSharpCode.Decompiler.ILAst
 						if (condBranch.Match(ILCode.Switch, out caseLabels)) {
 							
 							ILSwitch ilSwitch = new ILSwitch() { Condition = condBranch.Arguments.Single() };
-							result.Add(new ILBasicBlock() {
+							ILBasicBlock newBB = new ILBasicBlock() {
 								EntryLabel = block.EntryLabel,  // Keep the entry label
 								Body = { ilSwitch },
 								FallthoughGoto = block.FallthoughGoto
-							});
+							};
+							result.Add(newBB);
 
 							// Remove the item so that it is not picked up as content
 							scope.RemoveOrThrow(node);
 							
 							// Pull in code of cases
+							ILLabel fallLabel = (ILLabel)block.FallthoughGoto.Operand;
 							ControlFlowNode fallTarget = null;
-							labelToCfNode.TryGetValue((ILLabel)block.FallthoughGoto.Operand, out fallTarget);
+							labelToCfNode.TryGetValue(fallLabel, out fallTarget);
 							
 							HashSet<ControlFlowNode> frontiers = new HashSet<ControlFlowNode>();
 							if (fallTarget != null)
@@ -614,7 +616,10 @@ namespace ICSharpCode.Decompiler.ILAst
 								// Find or create new case block
 								ILSwitch.CaseBlock caseBlock = ilSwitch.CaseBlocks.Where(b => b.EntryGoto.Operand == condLabel).FirstOrDefault();
 								if (caseBlock == null) {
-									caseBlock = new ILSwitch.CaseBlock() { EntryGoto = new ILExpression(ILCode.Br, condLabel) };
+									caseBlock = new ILSwitch.CaseBlock() {
+										Values = new List<int>(),
+										EntryGoto = new ILExpression(ILCode.Br, condLabel)
+									};
 									ilSwitch.CaseBlocks.Add(caseBlock);
 									
 									ControlFlowNode condTarget = null;
@@ -629,6 +634,21 @@ namespace ICSharpCode.Decompiler.ILAst
 								}
 								caseBlock.Values.Add(i);
 							}
+							
+							// Heuristis to determine if we want to use fallthough as default case
+							if (fallTarget != null && !frontiers.Contains(fallTarget)) {
+								HashSet<ControlFlowNode> content = FindDominatedNodes(scope, fallTarget);
+								if (content.Any()) {
+									var caseBlock = new ILSwitch.CaseBlock() { EntryGoto = new ILExpression(ILCode.Br, fallLabel) };
+									ilSwitch.CaseBlocks.Add(caseBlock);
+									newBB.FallthoughGoto = null;
+								
+									scope.ExceptWith(content);
+									caseBlock.Body.AddRange(FindConditions(content, fallTarget));
+									// Add explicit break which should not be used by default, but the goto removal might decide to use it
+									caseBlock.Body.Add(new ILBasicBlock() { Body = { new ILExpression(ILCode.LoopOrSwitchBreak, null) } });
+								}
+							}
 						}
 						
 						// Two-way branch

ICSharpCode.Decompiler/ILAst/ILAstTypes.cs

@@ -444,7 +444,7 @@ namespace ICSharpCode.Decompiler.ILAst
 	{
 		public class CaseBlock: ILBlock
 		{
-			public List<int> Values = new List<int>();
+			public List<int> Values;  // null for the default case
 			
 			public override void WriteTo(ITextOutput output)
 			{

NRefactory/ICSharpCode.NRefactory/CSharp/OutputVisitor/OutputVisitor.cs

@@ -1529,8 +1529,13 @@ namespace ICSharpCode.NRefactory.CSharp
 		public object VisitSwitchSection(SwitchSection switchSection, object data)
 		{
 			StartNode(switchSection);
-			foreach (var label in switchSection.CaseLabels)
+			bool first = true;
+			foreach (var label in switchSection.CaseLabels) {
+				if (!first)
+					NewLine();
 				label.AcceptVisitor(this, data);
+				first = false;
+			}
 			foreach (var statement in switchSection.Statements)
 				statement.AcceptVisitor(this, data);
 			return EndNode(switchSection);
@@ -1539,11 +1544,14 @@ namespace ICSharpCode.NRefactory.CSharp
 		public object VisitCaseLabel(CaseLabel caseLabel, object data)
 		{
 			StartNode(caseLabel);
-			WriteKeyword("case");
-			Space();
-			caseLabel.Expression.AcceptVisitor(this, data);
+			if (caseLabel.Expression.IsNull) {
+				WriteKeyword("default");
+			} else {
+				WriteKeyword("case");
+				Space();
+				caseLabel.Expression.AcceptVisitor(this, data);
+			}
 			WriteToken(":", CaseLabel.Roles.Colon);
-			NewLine();
 			return EndNode(caseLabel);
 		}