Fix #1712: Invalid SequencePointsBlob when generating PDB: Filter duplicate IL range assignments.

ICSharpCode.Decompiler/CSharp/SequencePointBuilder.cs

@@ -300,7 +300,7 @@ namespace ICSharpCode.Decompiler.CSharp
 					if (sequencePoint.Offset < pos) {
 						// overlapping sequence point?
 						// delete previous sequence points that are after sequencePoint.Offset
-						while (newList.Count > 0 && newList.Last().EndOffset > pos) {
+						while (newList.Count > 0 && newList.Last().EndOffset > sequencePoint.Offset) {
 							var last = newList.Last();
 							if (last.Offset >= sequencePoint.Offset) {
 								newList.RemoveAt(newList.Count - 1);

ICSharpCode.Decompiler/DebugInfo/SequencePoint.cs

@@ -17,12 +17,14 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Diagnostics;
 
 namespace ICSharpCode.Decompiler.DebugInfo
 {
 	/// <summary>
 	/// A sequence point read from a PDB file or produced by the decompiler.
 	/// </summary>
+	[DebuggerDisplay("SequencePoint IL_{Offset,h}-IL_{EndOffset,h}, {StartLine}:{StartColumn}-{EndLine}:{EndColumn}, IsHidden={IsHidden}")]
 	public struct SequencePoint
 	{
 		/// <summary>