Cover PdbGen loops and ordered residuals

The PDB sequence-point tests were missing real while-loop input, and their residual comparison treated breakpoint locations as an unordered multiset. Add coverage for while/do-while fixtures and compare residuals in sequence order so stepping-order changes are pinned.

Assisted-by: CodeAlta:gpt-5.5:CodeAlta

ICSharpCode.Decompiler.Tests/Helpers/PdbSequencePoints.cs

@@ -16,6 +16,7 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -136,17 +137,13 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 				var expectedPoints = Tokens(expected, row, includeColumns, includeHidden);
 				var actualPoints = Tokens(actual, row, includeColumns, includeHidden);
 
-				var expectedOnly = MultisetDifference(expectedPoints, actualPoints);
-				var actualOnly = MultisetDifference(actualPoints, expectedPoints);
-				if (expectedOnly.Count == 0 && actualOnly.Count == 0)
+				if (expectedPoints.SequenceEqual(actualPoints))
 					continue;
 
 				methodNames.TryGetValue(row, out var name);
 				report.Append($"0x{0x06000000 | row:x8} {name}").Append('\n');
-				foreach (var p in expectedOnly.OrderBy(p => p))
-					report.Append("  - compiler only: ").Append(p).Append('\n');
-				foreach (var p in actualOnly.OrderBy(p => p))
-					report.Append("  + decompiler only: ").Append(p).Append('\n');
+				foreach (var (prefix, point) in OrderedDifference(expectedPoints, actualPoints))
+					report.Append(prefix).Append(point).Append('\n');
 			}
 			return report.ToString();
 		}
@@ -178,18 +175,37 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			return result;
 		}
 
-		static List<string> MultisetDifference(List<string> a, List<string> b)
+		static List<(string Prefix, string Point)> OrderedDifference(List<string> expected, List<string> actual)
 		{
-			var counts = new Dictionary<string, int>();
-			foreach (var x in b)
-				counts[x] = counts.GetValueOrDefault(x) + 1;
-			var result = new List<string>();
-			foreach (var x in a)
+			int[,] lcs = new int[expected.Count + 1, actual.Count + 1];
+			for (int i = expected.Count - 1; i >= 0; i--)
+			{
+				for (int j = actual.Count - 1; j >= 0; j--)
+				{
+					lcs[i, j] = expected[i] == actual[j]
+						? lcs[i + 1, j + 1] + 1
+						: Math.Max(lcs[i + 1, j], lcs[i, j + 1]);
+				}
+			}
+
+			var result = new List<(string Prefix, string Point)>();
+			for (int i = 0, j = 0; i < expected.Count || j < actual.Count;)
 			{
-				if (counts.TryGetValue(x, out int c) && c > 0)
-					counts[x] = c - 1;
+				if (i < expected.Count && j < actual.Count && expected[i] == actual[j])
+				{
+					i++;
+					j++;
+				}
+				else if (j < actual.Count && (i == expected.Count || lcs[i, j + 1] >= lcs[i + 1, j]))
+				{
+					result.Add(("  + decompiler only: ", actual[j]));
+					j++;
+				}
 				else
-					result.Add(x);
+				{
+					result.Add(("  - compiler only: ", expected[i]));
+					i++;
+				}
 			}
 			return result;
 		}

ICSharpCode.Decompiler.Tests/PdbGenerationTestRunner.cs

@@ -94,7 +94,9 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void WhileLoops()
 		{
-			TestSequencePoints();
+			// The compiler keeps the while-condition back-branch hidden, while the decompiler
+			// projects the loop condition and body points onto the decompiled source layout.
+			TestSequencePoints(knownResidual: true);
 		}
 
 		[Test]

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/AsyncAwait.residual.txt

@@ -1,7 +1,7 @@
 0x06000003 <SumAsync>d__0.MoveNext
-  - compiler only: (12,2)-(12,3)
-  - compiler only: hidden after (12,2)-(12,3)
+  + decompiler only: (7,2)-(7,3)
   - compiler only: hidden at method start
   - compiler only: hidden at method start
-  + decompiler only: (7,2)-(7,3)
   + decompiler only: hidden after (9,3)-(9,19)
+  - compiler only: (12,2)-(12,3)
+  - compiler only: hidden after (12,2)-(12,3)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/ForeachUsing.residual.txt

@@ -1,7 +1,7 @@
 0x06000001 ForeachUsing.Run
-  - compiler only: (17,2)-(17,3)
+  + decompiler only: (9,3)-(9,57)
   - compiler only: (9,10)-(9,56)
   - compiler only: hidden after (12,3)-(12,4)
-  - compiler only: hidden after (13,21)-(13,23)
   - compiler only: hidden after (13,24)-(13,29)
-  + decompiler only: (9,3)-(9,57)
+  - compiler only: hidden after (13,21)-(13,23)
+  - compiler only: (17,2)-(17,3)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/LambdaCapturing.residual.txt

@@ -1,8 +1,8 @@
 0x06000001 ICSharpCode.Decompiler.Tests.TestCases.PdbGen.LambdaCapturing.Main
-  - compiler only: hidden at method start
   + decompiler only: (8,2)-(8,3)
-  + decompiler only: hidden after (10,3)-(10,46)
   + decompiler only: hidden after (8,2)-(8,3)
+  - compiler only: hidden at method start
   + decompiler only: hidden after (9,3)-(9,15)
+  + decompiler only: hidden after (10,3)-(10,46)
 0x06000005 <>c__DisplayClass0_0.<Main>b__0
   + decompiler only: hidden after (11,26)-(11,42)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/LinqQuery.residual.txt

@@ -1,6 +1,6 @@
 0x06000001 LinqQuery.Run
-  - compiler only: (15,2)-(15,3)
   - compiler only: hidden after (9,21)-(9,23)
+  - compiler only: (15,2)-(15,3)
 0x06000005 <>c.<Run>b__0_0
   + decompiler only: hidden after (10,10)-(10,15)
 0x06000006 <>c.<Run>b__0_1

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/LockStatement.residual.txt

@@ -1,6 +1,6 @@
 0x06000001 LockStatement.Run
-  - compiler only: (13,2)-(13,3)
-  - compiler only: hidden after (12,3)-(12,4)
   + decompiler only: (10,3)-(10,4)
+  - compiler only: hidden after (12,3)-(12,4)
+  - compiler only: (13,2)-(13,3)
 0x06000003 LockStatement..cctor
   - compiler only: (5,2)-(5,53)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/Members.residual.txt

@@ -3,11 +3,11 @@
 0x06000004 C.get_Item
   + decompiler only: hidden after (18,31)-(18,35)
 0x0600000b C..ctor
-  - compiler only: (50,2)-(50,12)
   + decompiler only: (51,2)-(51,3)
+  - compiler only: (50,2)-(50,12)
 0x0600000c C.Finalize
   - compiler only: (56,2)-(56,3)
-  - compiler only: (57,2)-(57,3)
   + decompiler only: hidden after (57,2)-(57,3)
+  - compiler only: (57,2)-(57,3)
 0x0600000e C.Main
   + decompiler only: hidden after (66,3)-(68,5)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/SwitchExpression.residual.txt

@@ -1,7 +1,7 @@
 0x06000001 SwitchExpression.Classify
+  + decompiler only: (4,2)-(4,3)
+  + decompiler only: hidden after (5,3)-(10,5)
   - compiler only: (7,9)-(7,15)
   - compiler only: (8,9)-(8,14)
   - compiler only: (9,9)-(9,15)
   - compiler only: hidden after (9,9)-(9,15)
-  + decompiler only: (4,2)-(4,3)
-  + decompiler only: hidden after (5,3)-(10,5)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/SwitchStatement.residual.txt

@@ -1,5 +1,5 @@
 0x06000001 SwitchStatement.Classify
-  - compiler only: hidden at method start
   + decompiler only: (6,2)-(6,3)
   + decompiler only: (7,3)-(7,13)
   + decompiler only: hidden after (7,3)-(7,13)
+  - compiler only: hidden at method start

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/TryCatchFinally.residual.txt

@@ -1,5 +1,5 @@
 0x06000001 TryCatchFinally.Run
-  - compiler only: (23,2)-(23,3)
-  - compiler only: hidden after (15,21)-(15,33)
   + decompiler only: (16,3)-(16,4)
+  - compiler only: hidden after (15,21)-(15,33)
   + decompiler only: hidden after (22,3)-(22,4)
+  - compiler only: (23,2)-(23,3)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/UsingDeclaration.residual.txt

@@ -1,8 +1,8 @@
 0x06000001 UsingDeclaration.Run
-  - compiler only: (11,2)-(11,3)
-  - compiler only: (11,2)-(11,3)
+  + decompiler only: (8,3)-(8,55)
   - compiler only: (8,3)-(8,56)
+  + decompiler only: hidden after (10,3)-(10,46)
+  - compiler only: (11,2)-(11,3)
   - compiler only: hidden after (11,2)-(11,3)
   - compiler only: hidden after (11,2)-(11,3)
-  + decompiler only: (8,3)-(8,55)
-  + decompiler only: hidden after (10,3)-(10,46)
+  - compiler only: (11,2)-(11,3)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/WhileLoops.cs

@@ -0,0 +1,25 @@
+using System;
+
+internal class WhileLoops
+{
+	public static void PrintWhile(string[] args)
+	{
+		int i = 0;
+		while (i < args.Length)
+		{
+			Console.WriteLine(args[i]);
+			i++;
+		}
+	}
+
+	public static void PrintDoWhile(int count)
+	{
+		int i = 0;
+		do
+		{
+			Console.WriteLine(i);
+			i++;
+		}
+		while (i < count);
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/WhileLoops.residual.txt

@@ -0,0 +1,23 @@
+0x06000001 WhileLoops.PrintWhile
+  + decompiler only: (7,8)-(7,17)
+  + decompiler only: (9,4)-(9,31)
+  + decompiler only: (7,36)-(7,39)
+  + decompiler only: (7,19)-(7,34)
+  + decompiler only: (11,2)-(11,3)
+  - compiler only: (7,3)-(7,13)
+  - compiler only: hidden after (7,3)-(7,13)
+  - compiler only: (10,4)-(10,31)
+  - compiler only: (11,4)-(11,8)
+  - compiler only: (8,3)-(8,26)
+  - compiler only: (13,2)-(13,3)
+0x06000002 WhileLoops.PrintDoWhile
+  + decompiler only: (15,3)-(15,15)
+  + decompiler only: (18,4)-(18,27)
+  + decompiler only: (19,4)-(19,10)
+  + decompiler only: (21,3)-(21,22)
+  + decompiler only: (22,2)-(22,3)
+  - compiler only: (17,3)-(17,13)
+  - compiler only: (20,4)-(20,25)
+  - compiler only: (21,4)-(21,8)
+  - compiler only: (23,3)-(23,21)
+  - compiler only: (24,2)-(24,3)

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/YieldReturn.residual.txt

@@ -1,6 +1,6 @@
 0x06000005 <Range>d__0.MoveNext
-  - compiler only: hidden at method start
   + decompiler only: (7,2)-(7,3)
   + decompiler only: hidden after (7,2)-(7,3)
-  + decompiler only: hidden after (8,19)-(8,28)
+  - compiler only: hidden at method start
   + decompiler only: hidden after (8,30)-(8,33)
+  + decompiler only: hidden after (8,19)-(8,28)