Fix #1392: LoopDetection should take switch block containers into account in IncludeNestedContainers.

ICSharpCode.Decompiler.Tests/TestCases/Correctness/Loops.cs

@@ -259,5 +259,23 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
 			}
 			return num;
 		}
+
+		static void Issue1392ForWithNestedSwitchPlusGoto()
+		{
+			for (int i = 0; i < 100; i++) {
+				again:
+				switch (i) {
+					case 10:
+						Console.WriteLine("10");
+						break;
+					case 25:
+						Console.WriteLine("25");
+						break;
+					case 50:
+						Console.WriteLine("50");
+						goto again;
+				}
+			}
+		}
 	}
 }

ICSharpCode.Decompiler/IL/ControlFlow/LoopDetection.cs

@@ -142,7 +142,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 
 			void IncludeBlock(Block block)
 			{
-				if (block.Instructions[0] is BlockContainer nestedContainer) {
+				foreach (var nestedContainer in block.Instructions.OfType<BlockContainer>()) {
 					// Just in case the block has multiple nested containers (e.g. due to loop and switch),
 					// also check the entry point:
 					IncludeBlock(nestedContainer.EntryPoint);