use new exit lable

src/Nitload.RegularAnalysis/Text/TextRegexSourceGen.ExitLabel.cs

@@ -16,12 +16,15 @@ namespace Nitload.RegularAnalysis.Text
     internal partial class TextRegexSourceGen
     {
 
-        internal enum ExitMode
+        internal enum ExitKind
         {
 
-            Break,
+            MatchFailed,
-            Continue,
+            MatchEnd,
-            Goto,
+            CountRetry,
+            CountResume,
+            AltNext,
+            AltMatched,
 
         }
 
@@ -29,25 +32,28 @@ namespace Nitload.RegularAnalysis.Text
         {
 
             public ExitLabel(
-                   ExitMode mode,
+                   ExitKind kind,
                    int order
             )
             {
-                Mode = mode;
+                Kind = kind;
                 LabelOrder = order;
             }
 
-            public ExitMode Mode { get; init; }
+            public ExitKind Kind { get; init; }
 
             public int LabelOrder { get; init; }
 
             public string GetLabelName()
             {
-                return Mode switch
+                return Kind switch
                 {
-                    ExitMode.Break => $@"__break_{LabelOrder}",
+                    ExitKind.MatchFailed => $@"__match_failed_{LabelOrder}",
-                    ExitMode.Continue => $@"__continue_{LabelOrder}",
+                    ExitKind.MatchEnd => $@"__match_end_{LabelOrder}",
-                    ExitMode.Goto => $@"__goto_{LabelOrder}",
+                    ExitKind.CountRetry => $@"__count_retry_{LabelOrder}",
+                    ExitKind.CountResume => $@"__count_resume_{LabelOrder}",
+                    ExitKind.AltNext => $@"__alt_next_{LabelOrder}",
+                    ExitKind.AltMatched => $@"__alt_matched_{LabelOrder}",
                     _ => throw new NotImplementedException(),
                 };
             }

src/Nitload.RegularAnalysis/Text/TextRegexSourceGen.GenClass.cs

@@ -14,20 +14,31 @@ namespace Nitload.RegularAnalysis.Text
     internal partial class TextRegexSourceGen
     {
 
+        /// <summary>
+        ///   Emits a subtree and updates the retry target for the rest of the current path.
+        /// </summary>
+        /// <remarks>
+        ///   local_fail is the owning region's fallback. backtrack starts at that fallback and
+        ///   advances when a COUNT registers a retry point. Returning from recursion does not
+        ///   discard it. Mutually exclusive branches must use separate backtrack variables.
+        /// </remarks>
         internal static void GenerateMethodSource(
                              RegexAstNode ast,
                              in SequenceEmitter<string> sc,
                              in List<SequenceEmitter<string>> func_list,
                              in SourceGenContext context,
-                             in ExitLabel exit_label = default,
+                             in ExitLabel local_fail,
+                             ref ExitLabel backtrack,
                              bool is_find = false
         )
         {
+            // local_fail belongs to this region. COUNT updates only the current path's
+            // backtrack target; CONCAT passes that update on to every later sibling.
             RegexAstNode root = ast;
             if (root.Label == RegexElementLabel.EPSILON) {
                 return;
             }
-            if (TryGenerateSpecialSource(root, sc, func_list, context, exit_label)) {
+            if (TryGenerateSpecialSource(root, sc, func_list, context, local_fail, ref backtrack)) {
                 return;
             }
             RegexElementLabel op = root.Label & (RegexElementLabel.VAST_OPERATOR);
@@ -36,16 +47,16 @@ namespace Nitload.RegularAnalysis.Text
                 switch (op)
                 {
                     case RegexElementLabel.CONCAT:
-                        GenerateConcat(root, sc, func_list, context, exit_label);
+                        GenerateConcat(root, sc, func_list, context, local_fail, ref backtrack);
                         break;
                     case RegexElementLabel.COUNT:
-                        GenerateCount(root, sc, func_list, context, exit_label);
+                        GenerateCount(root, sc, func_list, context, local_fail, ref backtrack);
                         break;
                     case RegexElementLabel.GROUP_BEGIN:
-                        GenerateGroup(root, sc, func_list, context, exit_label);
+                        GenerateGroup(root, sc, func_list, context, local_fail, ref backtrack);
                         break;
                     case RegexElementLabel.ALT:
-                        GenerateAlt(root, sc, func_list, context, exit_label);
+                        GenerateAlt(root, sc, func_list, context, backtrack);
                         break;
                     default:
 
@@ -59,13 +70,13 @@ namespace Nitload.RegularAnalysis.Text
                 switch (op)
                 {
                     case RegexElementLabel.UNIT:
-                        GenerateUnit(root, sc, context, exit_label);
+                        GenerateUnit(root, sc, context, backtrack);
                         break;
                     case RegexElementLabel.UNIT_SET:
-                        GenerateUnitSet(root, sc, context, exit_label);
+                        GenerateUnitSet(root, sc, context, backtrack);
                         break;
                     case RegexElementLabel.UNIT_SPAN:
-                        GenerateUnitSpan(root, sc, context, exit_label);
+                        GenerateUnitSpan(root, sc, context, backtrack);
                         break;
                     default:
                         break;
@@ -220,11 +231,9 @@ namespace Nitload.RegularAnalysis.Text
                             int max,
                             bool is_greedy,
                             [NotNull] in SequenceEmitter<string> sc,
-                            in List<SequenceEmitter<string>> func_list,
                             in SourceGenContext context,
                             in ExitLabel exit,
-                            IReadOnlyList<RegexAstNode>? continuation = null,
+                            ref ExitLabel backtrack
-                            int next = 0
         )
         {
             if (min < 0 || (max >= 0 && max < min)) {
@@ -303,61 +312,54 @@ namespace Nitload.RegularAnalysis.Text
             }
 
             int additional_limit = max < 0 ? -1 : max - min;
-            bool has_continuation = continuation is not null && next < continuation.Count;
+            if (additional_limit == 0) {
-            bool can_retry = has_continuation && additional_limit != 0;
+                return;
+            }
+
+            // Save the optional portion once. Its counter is shared by scanning and retries.
             string additional_entry = $"__additional_entry_{scratch_scope_index}";
-            if (can_retry) {
+            ExitLabel retry = context.RequestExitLabel(ExitKind.CountRetry);
-                _ = sc.AppendLine($"{ROS_char} {additional_entry} = {remain_span};");
+            ExitLabel resume = context.RequestExitLabel(ExitKind.CountResume);
-            }
+            _ = sc.AppendLine($"{ROS_char} {additional_entry} = {remain_span};")
-            if (can_retry || (is_greedy && additional_limit > 0)) {
+                  .AppendLine($"int {additional_count} = 0;");
-                _ = sc.AppendLine($"int {additional_count} = 0;");
+            if (is_greedy)
-            }
-            if (is_greedy && additional_limit != 0)
             {
                 string limit = additional_limit < 0 ? string.Empty :
                     $"{additional_count} < {additional_limit} && ";
                 _ = sc.AppendLine($"while ({limit}!{remain_span}.IsEmpty && {remain_span}[0] == {expected_literal})")
                       .AppendLine("{")
-                      .AppendLine($"{remain_span} = {remain_span}.Slice(1);");
+                      .AppendLine($"{remain_span} = {remain_span}.Slice(1);")
-                if (can_retry || additional_limit > 0) {
+                      .AppendLine($"{additional_count}++;")
-                    _ = sc.AppendLine($"{additional_count}++;");
+                      .AppendLine("}");
-                }
-                _ = sc.AppendLine("}");
             }
-            if (can_retry)
+
+            // Initial success skips retry handling. Later failures jump back here from anywhere
+            // in this path; exhaustion forwards to the target inherited before this COUNT.
+            _ = sc.AppendLine($"goto {resume.GetLabelName()};")
+                  .AppendLine($"{retry.GetLabelName()}: {{}}");
+            if (is_greedy)
             {
-                // The same optional count drives scanning and retries. Required units stay consumed.
+                _ = sc.AppendLine($"if ({additional_count} == 0)")
-                ExitLabel retry = context.RequestExitLabel(ExitMode.Goto);
-                _ = sc.AppendLine("while (true)")
                       .AppendLine("{")
-                      .AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count});");
+                      .AppendLine($"{remain_span} = {additional_entry};")
-                GenerateConcatTail(continuation!, next, sc, func_list, context, retry);
+                      .AppendLine($"goto {exit_label_node};")
-                _ = sc.AppendLine("break;")
+                      .AppendLine("}")
-                      .AppendLine($"{retry.GetLabelName()}: {{}}");
+                      .AppendLine($"{additional_count}--;");
-                if (is_greedy)
+            } else
-                {
+            {
-                    _ = sc.AppendLine($"if ({additional_count} == 0)")
+                string limit = additional_limit < 0 ? string.Empty :
-                          .AppendLine("{")
+                    $"{additional_count} == {additional_limit} || ";
-                          .AppendLine($"{remain_span} = {additional_entry};")
+                _ = sc.AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count});")
-                          .AppendLine($"goto {exit_label_node};")
+                      .AppendLine($"if ({limit}{remain_span}.IsEmpty || {remain_span}[0] != {expected_literal})")
-                          .AppendLine("}")
+                      .AppendLine("{")
-                          .AppendLine($"{additional_count}--;");
+                      .AppendLine($"{remain_span} = {additional_entry};")
-                } else
+                      .AppendLine($"goto {exit_label_node};")
-                {
+                      .AppendLine("}")
-                    string limit = additional_limit < 0 ? string.Empty :
+                      .AppendLine($"{additional_count}++;");
-                        $"{additional_count} == {additional_limit} || ";
-                    _ = sc.AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count});")
-                          .AppendLine($"if ({limit}{remain_span}.IsEmpty || {remain_span}[0] != {expected_literal})")
-                          .AppendLine("{")
-                          .AppendLine($"{remain_span} = {additional_entry};")
-                          .AppendLine($"goto {exit_label_node};")
-                          .AppendLine("}")
-                          .AppendLine($"{additional_count}++;");
-                }
-                _ = sc.AppendLine("}");
-            } else if (has_continuation) {
-                GenerateConcatTail(continuation!, next, sc, func_list, context, exit);
             }
+            _ = sc.AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count});")
+                  .AppendLine($"{resume.GetLabelName()}: {{}}");
+            backtrack = retry;
         }
 
         private static void GenerateUnitSetCount(
@@ -440,11 +442,9 @@ namespace Nitload.RegularAnalysis.Text
                             int max,
                             bool is_greedy,
                             [NotNull] in SequenceEmitter<string> sc,
-                            in List<SequenceEmitter<string>> func_list,
                             in SourceGenContext context,
                             in ExitLabel exit,
-                            IReadOnlyList<RegexAstNode>? continuation = null,
+                            ref ExitLabel backtrack
-                            int next = 0
         )
         {
             if (min < 0 || (max >= 0 && max < min)) {
@@ -554,61 +554,54 @@ namespace Nitload.RegularAnalysis.Text
             }
 
             int additional_limit = max < 0 ? -1 : max - min;
-            bool has_continuation = continuation is not null && next < continuation.Count;
+            if (additional_limit == 0) {
-            bool can_retry = has_continuation && additional_limit != 0;
+                return;
+            }
+
+            // Save the optional portion once. Its counter is shared by scanning and retries.
             string additional_entry = $"__additional_entry_{scratch_scope_index}";
-            if (can_retry) {
+            ExitLabel retry = context.RequestExitLabel(ExitKind.CountRetry);
-                _ = sc.AppendLine($"{ROS_char} {additional_entry} = {remain_span};");
+            ExitLabel resume = context.RequestExitLabel(ExitKind.CountResume);
-            }
+            _ = sc.AppendLine($"{ROS_char} {additional_entry} = {remain_span};")
-            if (can_retry || (is_greedy && additional_limit > 0)) {
+                  .AppendLine($"int {additional_count} = 0;");
-                _ = sc.AppendLine($"int {additional_count} = 0;");
+            if (is_greedy)
-            }
-            if (is_greedy && additional_limit != 0)
             {
                 string limit = additional_limit < 0 ? string.Empty :
                     $"{additional_count} < {additional_limit} && ";
                 _ = sc.AppendLine($"while ({limit}{remain_span}.{starts_with}({expected_literal}))")
                       .AppendLine("{")
-                      .AppendLine($"{remain_span} = {remain_span}.Slice({literal.Length});");
+                      .AppendLine($"{remain_span} = {remain_span}.Slice({literal.Length});")
-                if (can_retry || additional_limit > 0) {
+                      .AppendLine($"{additional_count}++;")
-                    _ = sc.AppendLine($"{additional_count}++;");
+                      .AppendLine("}");
-                }
-                _ = sc.AppendLine("}");
             }
-            if (can_retry)
+
+            // Initial success skips retry handling. Later failures jump back here from anywhere
+            // in this path; exhaustion forwards to the target inherited before this COUNT.
+            _ = sc.AppendLine($"goto {resume.GetLabelName()};")
+                  .AppendLine($"{retry.GetLabelName()}: {{}}");
+            if (is_greedy)
             {
-                // Each retry moves by a complete literal using the scan's own optional counter.
+                _ = sc.AppendLine($"if ({additional_count} == 0)")
-                ExitLabel retry = context.RequestExitLabel(ExitMode.Goto);
-                _ = sc.AppendLine("while (true)")
                       .AppendLine("{")
-                      .AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count} * {literal.Length});");
+                      .AppendLine($"{remain_span} = {additional_entry};")
-                GenerateConcatTail(continuation!, next, sc, func_list, context, retry);
+                      .AppendLine($"goto {exit_label_node};")
-                _ = sc.AppendLine("break;")
+                      .AppendLine("}")
-                      .AppendLine($"{retry.GetLabelName()}: {{}}");
+                      .AppendLine($"{additional_count}--;");
-                if (is_greedy)
+            } else
-                {
+            {
-                    _ = sc.AppendLine($"if ({additional_count} == 0)")
+                string limit = additional_limit < 0 ? string.Empty :
-                          .AppendLine("{")
+                    $"{additional_count} == {additional_limit} || ";
-                          .AppendLine($"{remain_span} = {additional_entry};")
+                _ = sc.AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count} * {literal.Length});")
-                          .AppendLine($"goto {exit_label_node};")
+                      .AppendLine($"if ({limit}!{remain_span}.{starts_with}({expected_literal}))")
-                          .AppendLine("}")
+                      .AppendLine("{")
-                          .AppendLine($"{additional_count}--;");
+                      .AppendLine($"{remain_span} = {additional_entry};")
-                } else
+                      .AppendLine($"goto {exit_label_node};")
-                {
+                      .AppendLine("}")
-                    string limit = additional_limit < 0 ? string.Empty :
+                      .AppendLine($"{additional_count}++;");
-                        $"{additional_count} == {additional_limit} || ";
-                    _ = sc.AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count} * {literal.Length});")
-                          .AppendLine($"if ({limit}!{remain_span}.{starts_with}({expected_literal}))")
-                          .AppendLine("{")
-                          .AppendLine($"{remain_span} = {additional_entry};")
-                          .AppendLine($"goto {exit_label_node};")
-                          .AppendLine("}")
-                          .AppendLine($"{additional_count}++;");
-                }
-                _ = sc.AppendLine("}");
-            } else if (has_continuation) {
-                GenerateConcatTail(continuation!, next, sc, func_list, context, exit);
             }
+            _ = sc.AppendLine($"{remain_span} = {additional_entry}.Slice({additional_count} * {literal.Length});")
+                  .AppendLine($"{resume.GetLabelName()}: {{}}");
+            backtrack = retry;
         }
 
             #endregion
@@ -630,7 +623,7 @@ namespace Nitload.RegularAnalysis.Text
                             in ExitLabel exit_label
         )
         {
-            ExitLabel success = context.RequestExitLabel(ExitMode.Goto);
+            ExitLabel success = context.RequestExitLabel(ExitKind.AltMatched);
             RegexAstNode current = node.Right;
             while (!RegexAstNode.IsNullOrEmpty(current))
             {
@@ -639,7 +632,7 @@ namespace Nitload.RegularAnalysis.Text
             }
 
             _ = sc.AppendLine($"goto {exit_label.GetLabelName()};")
-                  .AppendLine($"{success.GetLabelName()}: ;");
+                  .AppendLine($"{success.GetLabelName()}: {{}}");
         }
 
         private static void GenerateGroup(
@@ -647,7 +640,8 @@ namespace Nitload.RegularAnalysis.Text
                             [NotNull] in SequenceEmitter<string> sc,
                             in List<SequenceEmitter<string>> func_list,
                             in SourceGenContext context,
-                            in ExitLabel exit_label
+                            in ExitLabel local_fail,
+                            ref ExitLabel backtrack
         )
         {
             RegexAstNode left = node.Left;
@@ -661,10 +655,10 @@ namespace Nitload.RegularAnalysis.Text
             // TODO(NGRA): Snapshot the group start cursor and restore it when the child fails.
             if (!RegexAstNode.IsNullOrEmpty(left))
             {
-                GenerateMethodSource(left, sc, func_list, context, exit_label);
+                GenerateMethodSource(left, sc, func_list, context, local_fail, ref backtrack);
             } else
             if (!RegexAstNode.IsNullOrEmpty(right)) {
-                GenerateMethodSource(right, sc, func_list, context, exit_label);
+                GenerateMethodSource(right, sc, func_list, context, local_fail, ref backtrack);
             }
 
             string group_name = config.Name;
@@ -679,13 +673,16 @@ namespace Nitload.RegularAnalysis.Text
                             [NotNull] in SequenceEmitter<string> sc,
                             in List<SequenceEmitter<string>> func_list,
                             in SourceGenContext context,
-                            in ExitLabel exit_label = default
+                            in ExitLabel local_fail,
+                            ref ExitLabel backtrack
         )
         {
-            // Keep the complete suffix visible even when CONCAT is left-associated.
+            if (!RegexAstNode.IsNullOrEmpty(node.Left)) {
-            List<RegexAstNode> sequence = [];
+                GenerateMethodSource(node.Left, sc, func_list, context, local_fail, ref backtrack);
-            AppendConcatNodes(node, sequence);
+            }
-            GenerateConcatTail(sequence, 0, sc, func_list, context, exit_label);
+            if (!RegexAstNode.IsNullOrEmpty(node.Right)) {
+                GenerateMethodSource(node.Right, sc, func_list, context, local_fail, ref backtrack);
+            }
         }
 
         private static void GenerateCount(
@@ -693,9 +690,8 @@ namespace Nitload.RegularAnalysis.Text
                             [NotNull] in SequenceEmitter<string> sc,
                             in List<SequenceEmitter<string>> func_list,
                             in SourceGenContext context,
-                            in ExitLabel exit_label,
+                            in ExitLabel local_fail,
-                            IReadOnlyList<RegexAstNode>? continuation = null,
+                            ref ExitLabel backtrack
-                            int next = 0
         )
         {
             RegexAstNode value = RegexAstNode.IsNullOrEmpty(node.Left) ? node.Right : node.Left;
@@ -716,6 +712,7 @@ namespace Nitload.RegularAnalysis.Text
             int min = payload.Min;
             int max = payload.Max;
             bool is_greedy = payload.IsGreedy;
+            ExitLabel failure = backtrack;
 
             // TODO(NGRA-NAMING): Reserve exclusive names for future repetition/rollback state
             // across complex COUNT retries; recursive children must use the same method pool.
@@ -723,21 +720,19 @@ namespace Nitload.RegularAnalysis.Text
             {
                 // TODO(NGRA): Emit min/max repetition, zero-width progress protection, greedy vs.
                 // lazy ordering, and per-attempt rollback for a complex COUNT body.
-                GenerateMethodSource(value, sc, func_list, context, exit_label);
+                GenerateMethodSource(value, sc, func_list, context, local_fail, ref backtrack);
             } else
             {
                 switch (value.Label & RegexElementLabel.SEQUENCE)
                 {
                     case RegexElementLabel.UNIT:
-                        GenerateUnitCount(value, min, max, is_greedy, sc, func_list, context,
+                        GenerateUnitCount(value, min, max, is_greedy, sc, context, failure, ref backtrack);
-                                          exit_label, continuation, next);
                         return;
                     case RegexElementLabel.UNIT_SET:
-                        GenerateUnitSetCount(value, min, max, is_greedy, sc, context, exit_label);
+                        GenerateUnitSetCount(value, min, max, is_greedy, sc, context, failure);
                         break;
                     case RegexElementLabel.UNIT_SPAN:
-                        GenerateUnitSpanCount(value, min, max, is_greedy, sc, func_list, context,
+                        GenerateUnitSpanCount(value, min, max, is_greedy, sc, context, failure, ref backtrack);
-                                              exit_label, continuation, next);
                         return;
                     default:
 
@@ -746,9 +741,6 @@ namespace Nitload.RegularAnalysis.Text
                         break;
                 }
             }
-            if (continuation is not null) {
-                GenerateConcatTail(continuation, next, sc, func_list, context, exit_label);
-            }
         }
 
         #endregion

src/Nitload.RegularAnalysis/Text/TextRegexSourceGen.GenContext.cs

@@ -36,7 +36,7 @@ namespace Nitload.RegularAnalysis.Text
 
             public const string _remain_span = "__remain";
 
-            private int _max_exit_lable;
+            private int _exit_label_count;
 
             private int _scratch_scope_count;
 
@@ -54,12 +54,12 @@ namespace Nitload.RegularAnalysis.Text
             }
 
             public ExitLabel RequestExitLabel(
-                             ExitMode exitMode
+                             ExitKind kind
             )
             {
-                int index = _max_exit_lable;
+                int index = _exit_label_count;
-                _max_exit_lable++;
+                _exit_label_count++;
-                return new(exitMode, index);
+                return new(kind, index);
             }
 
             public int RequestScratchScopeIndex()

src/Nitload.RegularAnalysis/Text/TextRegexSourceGen.GenSpecial.cs

@@ -17,7 +17,8 @@ namespace Nitload.RegularAnalysis.Text
                             in SequenceEmitter<string> sc,
                             in List<SequenceEmitter<string>> func_list,
                             in SourceGenContext context,
-                            in ExitLabel exit_label
+                            in ExitLabel local_fail,
+                            ref ExitLabel backtrack
         )
         {
             // A special rule owns the entire matched subtree. Returning false leaves emission
@@ -25,7 +26,7 @@ namespace Nitload.RegularAnalysis.Text
             return node.Label switch
             {
                 RegexElementLabel.CONCAT => TryGenerateFindConcat(node, sc, func_list, context,
-                                                                  exit_label),
+                                                                  local_fail, ref backtrack),
                 _ => false,
             };
         }
@@ -166,10 +167,12 @@ namespace Nitload.RegularAnalysis.Text
                             in ExitLabel success
         )
         {
-            ExitLabel failure = context.RequestExitLabel(ExitMode.Goto);
+            ExitLabel failure = context.RequestExitLabel(ExitKind.AltNext);
             string entry = $"__alt_entry_{context.RequestScratchScopeIndex()}";
             _ = sc.AppendLine($"{ROS_char} {entry} = {context.RemainSpan};");
-            GenerateMethodSource(node, sc, func_list, context, failure);
+            // Keep branch-local retries isolated from both siblings and the caller's path.
+            ExitLabel branch_backtrack = failure;
+            GenerateMethodSource(node, sc, func_list, context, failure, ref branch_backtrack);
             _ = sc.AppendLine($"goto {success.GetLabelName()};")
                   .AppendLine($"{failure.GetLabelName()}:")
                   .AppendLine($"{context.RemainSpan} = {entry};");
@@ -180,50 +183,6 @@ namespace Nitload.RegularAnalysis.Text
 
             #endregion
 
-        #region CONCAT continuation
-
-        private static void AppendConcatNodes(
-                            RegexAstNode node,
-                            List<RegexAstNode> sequence
-        )
-        {
-            if (RegexAstNode.IsNullOrEmpty(node)) {
-                return;
-            }
-            if (node.Label == RegexElementLabel.CONCAT &&
-                !RegexAstNode.IsDotStar(node.Left) && !IsNamedFind(node))
-            {
-                AppendConcatNodes(node.Left, sequence);
-                AppendConcatNodes(node.Right, sequence);
-            } else {
-                sequence.Add(node);
-            }
-        }
-
-        private static void GenerateConcatTail(
-                            IReadOnlyList<RegexAstNode> sequence,
-                            int start,
-                            in SequenceEmitter<string> sc,
-                            in List<SequenceEmitter<string>> func_list,
-                            in SourceGenContext context,
-                            in ExitLabel exit_label
-        )
-        {
-            for (int i = start; i < sequence.Count; i++)
-            {
-                RegexAstNode node = sequence[i];
-                if (node.Label == RegexElementLabel.COUNT)
-                {
-                    // COUNT owns both its repetition and the continuation that may retry it.
-                    GenerateCount(node, sc, func_list, context, exit_label, sequence, i + 1);
-                    return;
-                }
-                GenerateMethodSource(node, sc, func_list, context, exit_label);
-            }
-        }
-
-        #endregion
-
         #region FIND concatenation
 
         private static bool TryGenerateFindConcat(
@@ -231,7 +190,8 @@ namespace Nitload.RegularAnalysis.Text
                             in SequenceEmitter<string> sc,
                             in List<SequenceEmitter<string>> func_list,
                             in SourceGenContext context,
-                            in ExitLabel exit_label
+                            in ExitLabel local_fail,
+                            ref ExitLabel backtrack
         )
         {
             RegexAstNode left = node.Left;
@@ -246,7 +206,7 @@ namespace Nitload.RegularAnalysis.Text
             {
                 // TODO(NGRA): Emit the unnamed FIND candidate loop and retry the right subtree
                 // until it succeeds or no anchor candidate remains.
-                GenerateMethodSource(right, sc, func_list, context, exit_label, true);
+                GenerateMethodSource(right, sc, func_list, context, local_fail, ref backtrack, true);
                 return true;
             }
 
@@ -256,7 +216,7 @@ namespace Nitload.RegularAnalysis.Text
                 {
                     // TODO(NGRA): Emit named FIND retry and capture the text preceding the
                     // successful anchor candidate.
-                    GenerateMethodSource(right, sc, func_list, context, exit_label, true);
+                    GenerateMethodSource(right, sc, func_list, context, local_fail, ref backtrack, true);
                 } else
                 {
                     // TODO(NGRA): Capture the remaining input for a terminal named dot-star.

src/Nitload.RegularAnalysis/Text/TextRegexSourceGen.cs

@@ -172,7 +172,15 @@ namespace Nitload.RegularAnalysis.Text
             SequenceEmitter<string> methodSource = new();
             List<SequenceEmitter<string>> localFunctions = [];
 
-            GenerateMethodSource(root, methodSource, localFunctions, generationContext);
+            ExitLabel local_fail = generationContext.RequestExitLabel(ExitKind.MatchFailed);
+            ExitLabel backtrack = local_fail;
+            ExitLabel end = generationContext.RequestExitLabel(ExitKind.MatchEnd);
+            GenerateMethodSource(root, methodSource, localFunctions, generationContext,
+                                 local_fail, ref backtrack);
+            _ = methodSource.AppendLine($"goto {end.GetLabelName()};")
+                            .AppendLine($"{local_fail.GetLabelName()}: {{}}")
+                            .AppendLine("// TODO(NGRA): Produce the root failure result here.")
+                            .AppendLine($"{end.GetLabelName()}: {{}}");
             foreach (SequenceEmitter<string> localFunction in localFunctions) {
                 _ = methodSource.AppendLine()
                                 .AppendLine()

test/StgSharpDebug/TestRegexGenerate.cs

@@ -38,8 +38,14 @@ namespace Nitload
             SequenceEmitter<string> body = new();
             List<SequenceEmitter<string>> functions = [];
             SourceGenContext context = new();
-            ExitLabel exit = context.RequestExitLabel(ExitMode.Goto);
+            ExitLabel local_fail = context.RequestExitLabel(ExitKind.MatchFailed);
-            GenerateMethodSource(analysis.Ast.Root, body, functions, context, exit);
+            ExitLabel backtrack = local_fail;
+            ExitLabel end = context.RequestExitLabel(ExitKind.MatchEnd);
+            GenerateMethodSource(analysis.Ast.Root, body, functions, context, local_fail, ref backtrack);
+            _ = body.AppendLine($"goto {end.GetLabelName()};")
+                    .AppendLine($"{local_fail.GetLabelName()}: {{}}")
+                    .AppendLine("// TODO(NGRA): Produce the root failure result here.")
+                    .AppendLine($"{end.GetLabelName()}: {{}}");
 
             foreach (string line in body.ToList()) {
                 Console.WriteLine(line);