Fix #2983: display-class locals should be named uniquely per top-level ILFunction. Add assertion to ResolveCollisions: ensure that colliding/merged variables have the same type.

ICSharpCode.Decompiler/CSharp/Transforms/DeclareVariables.cs

@@ -476,6 +476,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					Debug.Assert(point1.level == point2.level);
 					if (point1.nextNode.Parent == point2.nextNode.Parent)
 					{
+						Debug.Assert(prev.Type.Equals(v.Type));
 						// We found a collision!
 						v.InvolvedInCollision = true;
 						prev.ReplacementDueToCollision = v;

ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs

@@ -58,6 +58,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		Dictionary<MethodDefinitionHandle, string> localFunctionMapping;
 		HashSet<ILVariable> loopCounters;
 		const char maxLoopVariableName = 'n';
+		int numDisplayClassLocals;
 
 		public void Run(ILFunction function, ILTransformContext context)
 		{
@@ -151,6 +152,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						AddExistingName(reservedVariableNames, p.Name);
 				}
 			}
+			numDisplayClassLocals = 0;
 			foreach (ILFunction f in function.Descendants.OfType<ILFunction>().Reverse())
 			{
 				PerformAssignment(f);
@@ -195,7 +197,6 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		{
 			// remove unused variables before assigning names
 			function.Variables.RemoveDead();
-			int numDisplayClassLocals = 0;
 			Dictionary<int, string> assignedLocalSignatureIndices = new Dictionary<int, string>();
 			foreach (var v in function.Variables.OrderBy(v => v.Name))
 			{