Reject C# continuation lines as declarations

TESTING_GUIDE.md

@@ -78,6 +78,7 @@ Use `docs/test-doc-maintenance-plan.md` before moving oversized suites or adding
   Console writer synchronization coverage yields between character writes instead of sleeping per character; use enough whole-line iterations to expose interleaving without adding wall-clock delay.
 - `SymbolExtractor*Tests.cs` and `ReferenceExtractor*Tests.cs`
   Extractor coverage is split by language or feature area with partial test classes, while shared helpers remain on the root `SymbolExtractorTests` / `ReferenceExtractorTests` parts.
+  C# declaration-boundary regressions should pair a direct extractor fixture with a real-index `symbols --exact-name` query. Keep invocation and parameter continuations beside valid multi-line methods, constructors, delegates, and local functions so both false-positive rejection and declaration ranges remain observable.
   Repository-metadata coverage lives in `SymbolExtractorRepositoryMetadataTests.cs` and `ReferenceExtractorRepositoryMetadataTests.cs`; keep TOML, JSON Lines, ignore/attributes, EditorConfig, `.rules`, and application-manifest capability assertions coordinated with conservative local-path and malformed-record controls.
   Capability-regression fixtures that require an unsupported language use the explicit `text` placeholder or an ambiguity bucket; do not use a recognized repository-metadata format as the unsupported control.
   When moving repeated extractor scenarios out of a giant suite, keep the new partial file grouped by a readable domain such as language, build-file format, or protocol surface, and prefer small semantic assertion helpers over repeated raw substring or predicate assertions.
@@ -968,6 +969,7 @@ dotnet test --filter "FullyQualifiedName~GitHelperTests"
   console writer synchronization coverageは文字writeごとのsleepではなくyieldを使い、wall-clock delayを追加せずinterleavingを露出できる十分なwhole-line iterationを維持してください。
 - `SymbolExtractor*Tests.cs` と `ReferenceExtractor*Tests.cs`
   extractor のカバレッジは言語または機能領域ごとの partial test class に分割し、共有 helper は root 側の `SymbolExtractorTests` / `ReferenceExtractorTests` に残します。
+  C# の declaration boundary に関する regression では、extractor を直接呼ぶ fixture と、実 index に対する `symbols --exact-name` query を組み合わせてください。呼び出し・parameter の continuation と、正当な複数行 method、constructor、delegate、local function を同居させ、false positive の拒否と宣言 range の両方を観測可能にします。
   repository metadata の coverage は `SymbolExtractorRepositoryMetadataTests.cs` と `ReferenceExtractorRepositoryMetadataTests.cs` に置きます。TOML、JSON Lines、ignore / attributes、EditorConfig、`.rules`、application manifest の capability assertion を、保守的な local-path 抽出と malformed-record control に同期させてください。
   未対応言語を必要とする capability regression fixture には明示的な `text` placeholder または ambiguity bucket を使い、認識済み repository metadata 形式を未対応 control に使わないでください。
   巨大 suite から繰り返しの extractor シナリオを切り出す場合は、言語、build-file 形式、protocol surface など読みやすい領域ごとの partial file にまとめ、raw substring や predicate assertion の繰り返しより小さな semantic assertion helper を優先してください。

changelog.d/unreleased/4831.fixed.md

@@ -0,0 +1,21 @@
+---
+category: fixed
+issues:
+  - 4831
+affected:
+  - src/CodeIndex/Indexer/Symbols/SymbolExtractor.ExtractCore.cs
+  - src/CodeIndex/Indexer/Symbols/SymbolExtractor.ExtractionPhases.cs
+  - src/CodeIndex/Indexer/Symbols/SymbolExtractor.LexicalScopes.cs
+  - src/CodeIndex/Indexer/Symbols/SymbolExtractor.Contracts.cs
+  - tests/CodeIndex.Tests/SymbolExtractorIssue4831Tests.cs
+  - tests/CodeIndex.Tests/QueryCommandRunnerIssue4831Tests.cs
+  - TESTING_GUIDE.md
+---
+
+## English
+
+- **C# declaration scanning now rejects expression and parameter continuations (#4831)** — The method and constructor scanner now checks a column-aware declaration-start scope before emitting symbols, so multi-line LINQ or fluent-call arguments no longer create duplicate function definitions and `out` / `params` parameter continuations no longer become functions. Block-lambda statement baselines preserve valid nested local functions, while reconciled conditional-compilation branch-end snapshots and ignored preprocessor payloads keep real methods visible across `#if` alternatives, disabled incomplete text, and arbitrary `#region` text. The C# extractor contract version invalidates stale rows, and focused extractor plus real-index exact-name tests prevent the continuation regressions previously covered by #496 and #4413 from returning.
+
+## 日本語
+
+- **C# の宣言走査で式と parameter の continuation を拒否するようにしました (#4831)** — method / constructor scanner は symbol を出力する前に列位置を考慮した declaration-start scope を確認するため、複数行の LINQ・fluent call 引数から重複 function 定義が生成されず、`out` / `params` の parameter continuation も function になりません。block lambda では statement baseline を設定して正当な入れ子 local function を維持し、conditional compilation では branch end ごとの snapshot を共通状態へreconcileし、preprocessor payload を無視することで、`#if` の代替分岐、無効化された未完了text、任意の `#region` text をまたいでも本物の method を維持します。C# extractor contract version で古い row を stale と判定し、extractor の focused test と実 index の exact-name test により #496 / #4413 で扱った continuation regression の再発を防ぎます。

src/CodeIndex/Indexer/Symbols/SymbolExtractor.Contracts.cs

@@ -5,7 +5,7 @@ public static partial class SymbolExtractor
     public const int DefaultContractVersion = 1;
     public const int ExpandedLanguageContractVersion = 2;
     public const int PythonContractVersion = 2;
-    public const int CSharpContractVersion = 6;
+    public const int CSharpContractVersion = 7;
     public const int DockerfileContractVersion = 2;
     public const int MakefileContractVersion = 2;
     public const int StyleAndXamlContractVersion = 2;

src/CodeIndex/Indexer/Symbols/SymbolExtractor.ExtractCore.cs

@@ -120,6 +120,7 @@ private static List<SymbolRecord> ExtractCore(
         var getPrivateScopeColumns = scanInputs.GetPrivateScopeColumns;
         Func<CSharpTypeBodyScope> GetCSharpInsideTypeBody = scanInputs.GetCSharpInsideTypeBody;
         Func<CSharpCallableParameterScope> GetCSharpCallableParameterScope = scanInputs.GetCSharpCallableParameterScope;
+        Func<CSharpDeclarationStartScope> GetCSharpDeclarationStartScope = scanInputs.GetCSharpDeclarationStartScope;
         var getCSharpSwitchExpressionLines = scanInputs.GetCSharpSwitchExpressionLines;
         var getCssQualifiedRuleAncestors = scanInputs.GetCssQualifiedRuleAncestors;
         var initialSymbolCapacity = EstimateSymbolListInitialCapacity(lines.Length);
@@ -465,6 +466,28 @@ private static List<SymbolRecord> ExtractCore(
                             continue;
                         }
 
+                        if (lang == "csharp"
+                            && pattern.Kind == "function"
+                            && pattern.BodyStyle == BodyStyle.Brace
+                            && !GetCSharpDeclarationStartScope().CanStartDeclarationAt(i, csharpGateRawStartColumn))
+                        {
+                            // Method and constructor patterns are intentionally broad enough to
+                            // recognize multi-line declarations. Do not let that merger begin from
+                            // an invocation argument or callable-parameter continuation, even when
+                            // a later declaration brace makes the combined text look method-shaped.
+                            // The scope is column-aware so a real same-line sibling remains eligible.
+                            // メソッドとコンストラクタのパターンは複数行宣言を認識するため意図的に
+                            // 広い。後続の宣言 brace によって結合テキストがメソッド形に見えても、
+                            // 呼び出し引数や callable parameter の継続位置から開始してはならない。
+                            // 列単位の scope により、同一行の後続にある本物の sibling は維持する。
+                            // Fixes #4831; prevents regressions covered by #496 and #4413.
+                            lineOffset = FindNextSameLineBraceStatementStart(
+                                matchLine,
+                                absoluteStartColumn + Math.Max(1, match.Length),
+                                lang);
+                            continue;
+                        }
+
                         if (lang == "csharp"
                             && pattern.Kind == "function"
                             && HasCSharpTokenBeforeIndex(matchLine, "when", absoluteStartColumn + match.Groups["name"].Index))

src/CodeIndex/Indexer/Symbols/SymbolExtractor.ExtractionPhases.cs

@@ -13,6 +13,7 @@ private sealed class PatternScanInputs
         private JavaScriptScopePrivacyFlags[][]? _privateScopeColumns;
         private CSharpTypeBodyScope? _csharpInsideTypeBody;
         private CSharpCallableParameterScope? _csharpCallableParameterScope;
+        private CSharpDeclarationStartScope? _csharpDeclarationStartScope;
         private bool[]? _csharpSwitchExpressionLines;
         private bool _csharpSwitchExpressionLinesInitialized;
         private bool[]? _cssQualifiedRuleAncestors;
@@ -119,6 +120,11 @@ public CSharpCallableParameterScope GetCSharpCallableParameterScope() =>
                 StructuralLines,
                 GetCSharpInsideTypeBody());
 
+        public CSharpDeclarationStartScope GetCSharpDeclarationStartScope() =>
+            _csharpDeclarationStartScope ??= BuildCSharpDeclarationStartScope(
+                StructuralLines,
+                GetCSharpInsideTypeBody());
+
         private CSharpLexState[] BuildCSharpLineStartStates() =>
             _csharpLineStartStates ??= SymbolExtractor.BuildCSharpLineStartStates(_lines);