Fix crash with null local scoperelease/5.0

2 files changed, 17 insertions, 24 deletions

diff --git a/Mono.Cecil.Cil/MethodBody.cs b/Mono.Cecil.Cil/MethodBody.cs
index 4aa71a9..d970a01 100644
--- a/Mono.Cecil.Cil/MethodBody.cs
+++ b/Mono.Cecil.Cil/MethodBody.cs
@@ -340,32 +340,11 @@ namespace Mono.Cecil.Cil {
 			UpdateLocalScope (debug_info.Scope, removedInstruction, existingInstruction, ref cache);
 		}
 
-		static void UpdateLocalScope (ScopeDebugInformation scope, int startFromOffset, int offset, Instruction instructionRemoved)
-		{
-			// For both start and enf offsets on the scope:
-			// * If the offset is resolved (points to instruction by reference)  only update it if the instruction it points to is being removed.
-			//   For non-removed instructions it remains correct regardless of any updates to the instructions.
-			// * If the offset is not resolved (stores the instruction offset number itself)
-			//   update the number accordingly to keep it pointing to the correct instruction (by offset).
-
-			if ((!scope.Start.IsResolved && scope.Start.Offset >= startFromOffset) || 
-				(instructionRemoved != null && scope.Start.ResolvedInstruction == instructionRemoved))
-				scope.Start = new InstructionOffset (scope.Start.Offset + offset);
-
-			// For end offset only update it if it's not the special sentinel value "EndOfMethod"; that should remain as-is.
-			if (!scope.End.IsEndOfMethod && 
-				((!scope.End.IsResolved && scope.End.Offset >= startFromOffset) ||
-				 (instructionRemoved != null && scope.End.ResolvedInstruction == instructionRemoved)))
-				scope.End = new InstructionOffset (scope.End.Offset + offset);
-
-			if (scope.HasScopes) {
-				foreach (var subScope in scope.Scopes)
-					UpdateLocalScope (subScope, startFromOffset, offset, instructionRemoved);
-			}
-		}
-
 		void UpdateLocalScope (ScopeDebugInformation scope, Instruction removedInstruction, Instruction existingInstruction, ref InstructionOffsetCache cache)
 		{
+			if (scope == null)
+				return;
+
 			if (!scope.Start.IsResolved)
 				scope.Start = ResolveInstructionOffset (scope.Start, ref cache);
 
diff --git a/Test/Mono.Cecil.Tests/ILProcessorTests.cs b/Test/Mono.Cecil.Tests/ILProcessorTests.cs
index 446e8fc..8836615 100644
--- a/Test/Mono.Cecil.Tests/ILProcessorTests.cs
+++ b/Test/Mono.Cecil.Tests/ILProcessorTests.cs
@@ -194,6 +194,20 @@ namespace Mono.Cecil.Tests {
 			methodBody.Method.Module.Dispose ();
 		}
 
+		[Test]
+		public void EditWithDebugInfoButNoLocalScopes()
+		{
+			var methodBody = CreateTestMethod (OpCodes.Ret);
+			methodBody.Method.DebugInformation = new MethodDebugInformation (methodBody.Method);
+
+			var il = methodBody.GetILProcessor ();
+			il.Replace (methodBody.Instructions [0], il.Create (OpCodes.Nop));
+
+			Assert.AreEqual (1, methodBody.Instructions.Count);
+			Assert.AreEqual (Code.Nop, methodBody.Instructions [0].OpCode.Code);
+			Assert.Null (methodBody.Method.DebugInformation.Scope);
+		}
+
 		static void AssertOpCodeSequence (OpCode [] expected, MethodBody body)
 		{
 			var opcodes = body.Instructions.Select (i => i.OpCode).ToArray ();