Fix #2182: Ensure that all labels generated by StatementBuilder are unique.

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -287,7 +287,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				{
 					if (caseLabelMapping.ContainsKey(block))
 						continue;
-					lastSectionStatements.Add(new LabelStatement { Label = block.Label });
+					lastSectionStatements.Add(new LabelStatement { Label = EnsureUniqueLabel(block) });
 					foreach (var nestedInst in block.Instructions)
 					{
 						var nestedStmt = Convert(nestedInst);
@@ -355,7 +355,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				return new GotoCaseStatement() { LabelExpression = exprBuilder.ConvertConstantValue(label, allowImplicitConversion: true) }
 					.WithILInstruction(inst);
 			}
-			return new GotoStatement(inst.TargetLabel).WithILInstruction(inst);
+			return new GotoStatement(EnsureUniqueLabel(inst.TargetBlock)).WithILInstruction(inst);
 		}
 
 		/// <summary>Target container that a 'break;' statement would break out of</summary>
@@ -1190,7 +1190,7 @@ namespace ICSharpCode.Decompiler.CSharp
 						// We'll also remove any "continue;" in front of the label, as it's redundant.
 						if (blockStatement.LastOrDefault() is ContinueStatement)
 							blockStatement.Last().Remove();
-						blockStatement.Add(new LabelStatement { Label = container.EntryPoint.Label });
+						blockStatement.Add(new LabelStatement { Label = EnsureUniqueLabel(container.EntryPoint) });
 					}
 
 					if (blockStatement.LastOrDefault() is ContinueStatement continueStmt2)
@@ -1214,7 +1214,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					{
 						// if there are branches to the condition block, that were not converted
 						// to continue statements, we have to introduce an extra label.
-						blockStatement.Add(new LabelStatement { Label = continueTarget.Label });
+						blockStatement.Add(new LabelStatement { Label = EnsureUniqueLabel(continueTarget) });
 					}
 					DeclareLocalFunctions(currentFunction, container, blockStatement);
 					if (blockStatement.Statements.Count == 0)
@@ -1249,7 +1249,7 @@ namespace ICSharpCode.Decompiler.CSharp
 						forStmt.Iterators.Add(Convert(continueTarget.Instructions[i]));
 					}
 					if (continueTarget.IncomingEdgeCount > continueCount)
-						blockStatement.Add(new LabelStatement { Label = continueTarget.Label });
+						blockStatement.Add(new LabelStatement { Label = EnsureUniqueLabel(continueTarget) });
 					DeclareLocalFunctions(currentFunction, container, blockStatement);
 					return forStmt;
 				default:
@@ -1309,7 +1309,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				if (block.IncomingEdgeCount > 1 || block != container.EntryPoint)
 				{
 					// If there are any incoming branches to this block, add a label:
-					blockStatement.Add(new LabelStatement { Label = block.Label });
+					blockStatement.Add(new LabelStatement { Label = EnsureUniqueLabel(block) });
 				}
 				foreach (var inst in block.Instructions)
 				{
@@ -1350,6 +1350,25 @@ namespace ICSharpCode.Decompiler.CSharp
 			return blockStatement;
 		}
 
+		readonly Dictionary<Block, string> labels = new Dictionary<Block, string>();
+		readonly Dictionary<string, int> duplicateLabels = new Dictionary<string, int>();
+
+		string EnsureUniqueLabel(Block block)
+		{
+			if (labels.TryGetValue(block, out string label))
+				return label;
+			if (!duplicateLabels.TryGetValue(block.Label, out int count))
+			{
+				labels.Add(block, block.Label);
+				duplicateLabels.Add(block.Label, 1);
+				return block.Label;
+			}
+			label = $"{block.Label}_{count + 1}";
+			duplicateLabels[block.Label]++;
+			labels.Add(block, label);
+			return label;
+		}
+
 		static bool IsFinalLeave(Leave leave)
 		{
 			if (!leave.Value.MatchNop())