Fix #3278: Missing variable declaration in nested for-loop after many other loops

ICSharpCode.Decompiler.Tests/TestCases/Pretty/VariableNaming.cs

@@ -88,5 +88,80 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			}
 #endif
 		}
+
+		private static void NestedForLoopTest2()
+		{
+			for (int i = 0; i < 10; i++)
+			{
+				Nop(i);
+			}
+#if EXPECTED_OUTPUT && !(LEGACY_CSC && !OPT)
+			for (int j = 0; j < 10; j++)
+			{
+				Nop(j);
+			}
+
+			for (int k = 0; k < 10; k++)
+			{
+				Nop(k);
+			}
+
+			for (int l = 0; l < 10; l++)
+			{
+				Nop(l);
+			}
+
+			for (int m = 0; m < 10; m++)
+			{
+				for (int n = 0; n < 10; n++)
+				{
+					Nop(n);
+				}
+			}
+
+			for (int num = 0; num < 10; num++)
+			{
+				for (int num2 = 0; num2 < 10; num2++)
+				{
+					Nop(num2);
+				}
+			}
+#else
+			for (int i = 0; i < 10; i++)
+			{
+				Nop(i);
+			}
+
+			for (int i = 0; i < 10; i++)
+			{
+				Nop(i);
+			}
+
+			for (int i = 0; i < 10; i++)
+			{
+				Nop(i);
+			}
+
+			for (int i = 0; i < 10; i++)
+			{
+				for (int j = 0; j < 10; j++)
+				{
+					Nop(j);
+				}
+			}
+
+			for (int i = 0; i < 10; i++)
+			{
+				for (int j = 0; j < 10; j++)
+				{
+					Nop(j);
+				}
+			}
+#endif
+		}
+
+		private static void Nop(int v)
+		{
+		}
 	}
 }

ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs

@@ -289,7 +289,6 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			string nameWithoutNumber = SplitName(newName, out int newIndex);
 			if (reservedVariableNames.TryGetValue(nameWithoutNumber, out int lastUsedIndex))
 			{
-				// name without number was already used
 				if (v.Type.IsKnownType(KnownTypeCode.Int32) && loopCounters.Contains(v))
 				{
 					// special case for loop counters,
@@ -298,8 +297,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					nameWithoutNumber = newName;
 					newIndex = 1;
 				}
-				else
+			}
+			if (reservedVariableNames.TryGetValue(nameWithoutNumber, out lastUsedIndex))
 			{
+				// name without number was already used
 				if (newIndex > lastUsedIndex)
 				{
 					// new index is larger than last, so we can use it
@@ -312,7 +313,6 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				// resolve conflicts by appending the index to the new name:
 				newName = nameWithoutNumber + newIndex.ToString();
 			}
-			}
 			// update the last used index
 			reservedVariableNames[nameWithoutNumber] = newIndex;
 			variableMapping.Add(v, newName);