Merge pull request #20425 from michaelnebel/csharp/basicextractoroverlay

C#: Overlay extraction support.

csharp/codeql-extractor.yml

@@ -4,6 +4,7 @@ aliases:
 display_name: "C#"
 version: 1.22.1
 column_kind: "utf16"
+overlay_support_version: 20250626
 extra_env_vars:
   DOTNET_GENERATE_ASPNET_CERTIFICATE: "false"
 build_modes:

csharp/downgrades/605f85053409cd72b4904df3f198ddc8324f3a83/upgrade.properties

@@ -0,0 +1,4 @@
+description: Delete databaseMetadata and overlayChangedFiles relations
+compatibility: full
+databaseMetadata.rel: delete
+overlayChangedFiles.rel: delete

csharp/downgrades/68b5aec54e50fe7e375df3777b756a746ca3a37c/upgrade.properties

@@ -0,0 +1,2 @@
+description: Remove @locatable type
+compatibility: full

csharp/extractor/Semmle.Extraction.CSharp.Standalone/Extractor.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.IO;
 using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -53,6 +54,20 @@ namespace Semmle.Extraction.CSharp.Standalone
                         }
 
                         progressMonitor.MissingSummary(analyser.ExtractionContext!.MissingTypes.Count(), analyser.ExtractionContext!.MissingNamespaces.Count());
+
+                        // If extracting a base database, we need to create an empty metadata file.
+                        if (EnvironmentVariables.GetBaseMetaDataOutPath() is string baseMetaDataOutPath)
+                        {
+                            try
+                            {
+                                analyser.Logger.LogInfo($"Creating base metadata file at {baseMetaDataOutPath}");
+                                File.WriteAllText(baseMetaDataOutPath, string.Empty);
+                            }
+                            catch (Exception ex)
+                            {
+                                analyser.Logger.LogError($"Failed to create base metadata file: {ex.Message}");
+                            }
+                        }
                     });
             }
             finally
@@ -143,7 +158,8 @@ namespace Semmle.Extraction.CSharp.Standalone
             var pathTransformer = new PathTransformer(canonicalPathCache);
 
             var progressMonitor = new ExtractionProgress(logger);
-            using var analyser = new StandaloneAnalyser(progressMonitor, fileLogger, pathTransformer, canonicalPathCache, false);
+            var overlayInfo = OverlayInfoFactory.Make(logger, options.SrcDir);
+            using var analyser = new StandaloneAnalyser(progressMonitor, fileLogger, pathTransformer, canonicalPathCache, overlayInfo, false);
             try
             {
                 var extractionInput = new ExtractionInput(dependencyManager.AllSourceFiles, dependencyManager.ReferenceFiles, dependencyManager.CompilationInfos);

csharp/extractor/Semmle.Extraction.CSharp/Entities/Attribute.cs

@@ -57,8 +57,21 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override void Populate(TextWriter trapFile)
         {
+            // In this case, we don't extract the attribute again, as it was extracted using * ID
+            // originally and we re-use that.
+            if (Context.OnlyScaffold && (ReportingLocation is null || !ReportingLocation.IsInSource))
+            {
+                return;
+            }
+
             var type = Type.Create(Context, Symbol.AttributeClass);
             trapFile.attributes(this, kind, type.TypeRef, entity);
+
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             WriteLocationToTrap(trapFile.attribute_location, this, Location);
 
             if (attributeSyntax is not null)

csharp/extractor/Semmle.Extraction.CSharp/Entities/CommentBlock.cs

@@ -10,9 +10,13 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override void Populate(TextWriter trapFile)
         {
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
             trapFile.commentblock(this);
-            WriteLocationToTrap(trapFile.commentblock_location, this, Context.CreateLocation(Symbol.Location));
             Symbol.CommentLines.ForEach((l, child) => trapFile.commentblock_child(this, l, child));
+            WriteLocationToTrap(trapFile.commentblock_location, this, Context.CreateLocation(Symbol.Location));
         }
 
         public override bool NeedsPopulation => true;
@@ -27,6 +31,10 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public void BindTo(Label entity, CommentBinding binding)
         {
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
             Context.TrapWriter.Writer.commentblock_binding(this, entity, binding);
         }
 

csharp/extractor/Semmle.Extraction.CSharp/Entities/CommentLine.cs

@@ -21,9 +21,14 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override void Populate(TextWriter trapFile)
         {
-            location = Context.CreateLocation(Location);
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
             trapFile.commentline(this, Type == CommentLineType.MultilineContinuation ? CommentLineType.Multiline : Type, Text, RawText);
+            location = Context.CreateLocation(Location);
             WriteLocationToTrap(trapFile.commentline_location, this, location);
+
         }
 
         public override Microsoft.CodeAnalysis.Location? ReportingLocation => location?.Symbol;

csharp/extractor/Semmle.Extraction.CSharp/Entities/Compilations/CompilerDiagnostic.cs

@@ -21,6 +21,11 @@ namespace Semmle.Extraction.CSharp.Entities
 
         protected override void Populate(TextWriter trapFile)
         {
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             var key = diagnostic.Id;
             var messageCount = compilation.messageCounts.AddOrUpdate(key, 1, (_, c) => c + 1);
             if (messageCount > limit)

csharp/extractor/Semmle.Extraction.CSharp/Entities/Constructor.cs

@@ -29,9 +29,17 @@ namespace Semmle.Extraction.CSharp.Entities
             ContainingType!.PopulateGenerics();
 
             trapFile.constructors(this, Symbol.ContainingType.Name, ContainingType, (Constructor)OriginalDefinition);
-            if (Context.ExtractLocation(Symbol) && (!IsDefault || IsBestSourceLocation))
+
+            if (Symbol.IsImplicitlyDeclared)
             {
-                WriteLocationToTrap(trapFile.constructor_location, this, Location);
+                var lineCounts = new LineCounts() { Total = 2, Code = 1, Comment = 0 };
+                trapFile.numlines(this, lineCounts);
+            }
+            ExtractCompilerGenerated(trapFile);
+
+            if (Context.OnlyScaffold)
+            {
+                return;
             }
 
             if (MakeSynthetic)
@@ -40,12 +48,11 @@ namespace Semmle.Extraction.CSharp.Entities
                 Statements.SyntheticEmptyBlock.Create(Context, this, 0, Location);
             }
 
-            if (Symbol.IsImplicitlyDeclared)
+            if (Context.ExtractLocation(Symbol) && (!IsDefault || IsBestSourceLocation))
             {
-                var lineCounts = new LineCounts() { Total = 2, Code = 1, Comment = 0 };
+                WriteLocationToTrap(trapFile.constructor_location, this, Location);
-                trapFile.numlines(this, lineCounts);
             }
-            ExtractCompilerGenerated(trapFile);
+
         }
 
         protected override void ExtractInitializers(TextWriter trapFile)
@@ -53,7 +60,7 @@ namespace Semmle.Extraction.CSharp.Entities
             // Do not extract initializers for constructed types.
             // Extract initializers for constructors with a body, primary constructors
             // and default constructors for classes and structs declared in source code.
-            if (Block is null && ExpressionBody is null && !MakeSynthetic)
+            if (Block is null && ExpressionBody is null && !MakeSynthetic || Context.OnlyScaffold)
             {
                 return;
             }
@@ -106,6 +113,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 }
 
                 var baseConstructorTarget = Create(Context, baseConstructor);
+
                 var info = new ExpressionInfo(Context,
                     AnnotatedTypeSymbol.CreateNotAnnotated(baseType),
                     Location,
@@ -179,7 +187,7 @@ namespace Semmle.Extraction.CSharp.Entities
         /// </summary>
         private bool IsBestSourceLocation => ReportingLocation is not null && Context.IsLocationInContext(ReportingLocation);
 
-        private bool MakeSynthetic => IsPrimary || (IsDefault && IsBestSourceLocation);
+        private bool MakeSynthetic => (IsPrimary || (IsDefault && IsBestSourceLocation)) && !Context.OnlyScaffold;
 
         [return: NotNullIfNotNull(nameof(constructor))]
         public static new Constructor? Create(Context cx, IMethodSymbol? constructor)

csharp/extractor/Semmle.Extraction.CSharp/Entities/Destructor.cs

@@ -15,6 +15,7 @@ namespace Semmle.Extraction.CSharp.Entities
             ContainingType!.PopulateGenerics();
 
             trapFile.destructors(this, $"~{Symbol.ContainingType.Name}", ContainingType, OriginalDefinition(Context, this, Symbol));
+
             if (Context.ExtractLocation(Symbol))
             {
                 WriteLocationToTrap(trapFile.destructor_location, this, Location);

csharp/extractor/Semmle.Extraction.CSharp/Entities/Event.cs

@@ -37,7 +37,6 @@ namespace Semmle.Extraction.CSharp.Entities
                 Method.Create(Context, remover);
 
             PopulateModifiers(trapFile);
-            BindComments();
 
             var declSyntaxReferences = IsSourceDeclaration
                 ? Symbol.DeclaringSyntaxReferences.Select(d => d.GetSyntax()).ToArray()
@@ -51,6 +50,13 @@ namespace Semmle.Extraction.CSharp.Entities
                     TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
+            BindComments();
+
             if (Context.ExtractLocation(Symbol))
             {
                 WriteLocationsToTrap(trapFile.event_location, this, Locations);

csharp/extractor/Semmle.Extraction.CSharp/Entities/ExtractionMessage.cs

@@ -28,6 +28,11 @@ namespace Semmle.Extraction.CSharp.Entities
 
         protected override void Populate(TextWriter trapFile)
         {
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             // For the time being we're counting the number of messages per severity, we could introduce other groupings in the future
             var key = msg.Severity.ToString();
             groupedMessageCounts.AddOrUpdate(key, 1, (_, c) => c + 1);

csharp/extractor/Semmle.Extraction.CSharp/Entities/Field.cs

@@ -49,6 +49,11 @@ namespace Semmle.Extraction.CSharp.Entities
                 }
             }
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             if (Context.ExtractLocation(Symbol))
             {
                 WriteLocationsToTrap(trapFile.field_location, this, Locations);

csharp/extractor/Semmle.Extraction.CSharp/Entities/Indexer.cs

@@ -19,10 +19,6 @@ namespace Semmle.Extraction.CSharp.Entities
 
             var type = Type.Create(Context, Symbol.Type);
             trapFile.indexers(this, Symbol.GetName(useMetadataName: true), ContainingType!, type.TypeRef, OriginalDefinition);
-            if (Context.ExtractLocation(Symbol))
-            {
-                WriteLocationsToTrap(trapFile.indexer_location, this, Locations);
-            }
 
             var getter = BodyDeclaringSymbol.GetMethod;
             var setter = BodyDeclaringSymbol.SetMethod;
@@ -42,20 +38,8 @@ namespace Semmle.Extraction.CSharp.Entities
                 Parameter.Create(Context, Symbol.Parameters[i], this, original);
             }
 
-            if (IsSourceDeclaration)
-            {
-                var expressionBody = ExpressionBody;
-                if (expressionBody is not null)
-                {
-                    // The expression may need to reference parameters in the getter.
-                    // So we need to arrange that the expression is populated after the getter.
-                    Context.PopulateLater(() => Expression.CreateFromNode(new ExpressionNodeInfo(Context, expressionBody, this, 0).SetType(Symbol.GetAnnotatedType())));
-                }
-            }
-
             PopulateAttributes();
             PopulateModifiers(trapFile);
-            BindComments();
 
             var declSyntaxReferences = IsSourceDeclaration
                 ? Symbol.DeclaringSyntaxReferences.
@@ -70,6 +54,28 @@ namespace Semmle.Extraction.CSharp.Entities
                     TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.indexer_location, this, Locations);
+            }
+
+            if (IsSourceDeclaration)
+            {
+                var expressionBody = ExpressionBody;
+                if (expressionBody is not null)
+                {
+                    // The expression may need to reference parameters in the getter.
+                    // So we need to arrange that the expression is populated after the getter.
+                    Context.PopulateLater(() => Expression.CreateFromNode(new ExpressionNodeInfo(Context, expressionBody, this, 0).SetType(Symbol.GetAnnotatedType())));
+                }
+            }
+
+            BindComments();
 
             foreach (var syntax in declSyntaxReferences)
                 TypeMention.Create(Context, syntax.Type, this, type);

csharp/extractor/Semmle.Extraction.CSharp/Entities/LocalVariable.cs

@@ -41,6 +41,11 @@ namespace Semmle.Extraction.CSharp.Entities
                 trapFile.localvars(this, Kinds.VariableKind.None, Symbol.Name, @var, Type.Create(Context, parent.Type).TypeRef, parent);
             }
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             WriteLocationToTrap(trapFile.localvar_location, this, Location);
 
             DefineConstantValue(trapFile);

csharp/extractor/Semmle.Extraction.CSharp/Entities/Method.cs

@@ -48,7 +48,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         protected virtual void PopulateMethodBody(TextWriter trapFile)
         {
-            if (!IsSourceDeclaration)
+            if (!IsSourceDeclaration || Context.OnlyScaffold)
                 return;
 
             var block = Block;

csharp/extractor/Semmle.Extraction.CSharp/Entities/NamespaceDeclaration.cs

@@ -35,7 +35,6 @@ namespace Semmle.Extraction.CSharp.Entities
 
             var ns = Namespace.Create(Context, @namespace);
             trapFile.namespace_declarations(this, ns);
-            WriteLocationToTrap(trapFile.namespace_declaration_location, this, Context.CreateLocation(node.Name.GetLocation()));
 
             var visitor = new Populators.TypeOrNamespaceVisitor(Context, trapFile, this);
 
@@ -48,6 +47,12 @@ namespace Semmle.Extraction.CSharp.Entities
             {
                 trapFile.parent_namespace_declaration(this, parent);
             }
+
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+            WriteLocationToTrap(trapFile.namespace_declaration_location, this, Context.CreateLocation(node.Name.GetLocation()));
         }
 
         public static NamespaceDeclaration Create(Context cx, BaseNamespaceDeclarationSyntax decl, NamespaceDeclaration parent)

csharp/extractor/Semmle.Extraction.CSharp/Entities/OrdinaryMethod.cs

@@ -34,6 +34,16 @@ namespace Semmle.Extraction.CSharp.Entities
             var returnType = Type.Create(Context, Symbol.ReturnType);
             trapFile.methods(this, Name, ContainingType, returnType.TypeRef, OriginalDefinition);
 
+            PopulateGenerics(trapFile);
+            Overrides(trapFile);
+            ExtractRefReturn(trapFile, Symbol, this);
+            ExtractCompilerGenerated(trapFile);
+
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             if (IsSourceDeclaration)
             {
                 foreach (var declaration in Symbol.DeclaringSyntaxReferences.Select(s => s.GetSyntax()).OfType<MethodDeclarationSyntax>())
@@ -47,11 +57,6 @@ namespace Semmle.Extraction.CSharp.Entities
             {
                 WriteLocationsToTrap(trapFile.method_location, this, Locations);
             }
-
-            PopulateGenerics(trapFile);
-            Overrides(trapFile);
-            ExtractRefReturn(trapFile, Symbol, this);
-            ExtractCompilerGenerated(trapFile);
         }
 
         private bool IsCompilerGeneratedDelegate() =>

csharp/extractor/Semmle.Extraction.CSharp/Entities/Parameter.cs

@@ -115,6 +115,11 @@ namespace Semmle.Extraction.CSharp.Entities
             var type = Type.Create(Context, Symbol.Type);
             trapFile.@params(this, Name, type.TypeRef, Ordinal, ParamKind, Parent!, Original);
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             if (Context.ExtractLocation(Symbol))
             {
                 var locations = Context.GetLocations(Symbol);

csharp/extractor/Semmle.Extraction.CSharp/Entities/PreprocessorDirectives/PreprocessorDirective.cs

@@ -13,10 +13,15 @@ namespace Semmle.Extraction.CSharp.Entities
             PopulatePreprocessor(trapFile);
 
             trapFile.preprocessor_directive_active(this, Symbol.IsActive);
-            WriteLocationToTrap(trapFile.preprocessor_directive_location, this, Context.CreateLocation(ReportingLocation));
 
             var compilation = Compilation.Create(Context);
             trapFile.preprocessor_directive_compilation(this, compilation);
+
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+            WriteLocationToTrap(trapFile.preprocessor_directive_location, this, Context.CreateLocation(ReportingLocation));
         }
 
         protected abstract void PopulatePreprocessor(TextWriter trapFile);

csharp/extractor/Semmle.Extraction.CSharp/Entities/Property.cs

@@ -40,7 +40,6 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             PopulateAttributes();
             PopulateModifiers(trapFile);
-            BindComments();
             PopulateNullability(trapFile, Symbol.GetAnnotatedType());
             PopulateRefKind(trapFile, Symbol.RefKind);
 
@@ -69,6 +68,13 @@ namespace Semmle.Extraction.CSharp.Entities
                     TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
+            BindComments();
+
             if (Context.ExtractLocation(Symbol))
             {
                 WriteLocationsToTrap(trapFile.property_location, this, Locations);

csharp/extractor/Semmle.Extraction.CSharp/Entities/TypeMention.cs

@@ -59,6 +59,11 @@ namespace Semmle.Extraction.CSharp.Entities
 
         protected override void Populate(TextWriter trapFile)
         {
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             switch (syntax.Kind())
             {
                 case SyntaxKind.ArrayType:

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/DynamicType.cs

@@ -16,10 +16,14 @@ namespace Semmle.Extraction.CSharp.Entities
         public override void Populate(TextWriter trapFile)
         {
             trapFile.types(this, Kinds.TypeKind.DYNAMIC, "dynamic");
-            WriteLocationToTrap(trapFile.type_location, this, Location);
 
             trapFile.has_modifiers(this, Modifier.Create(Context, "public"));
             trapFile.parent_namespace(this, Namespace.Create(Context, Context.Compilation.GlobalNamespace));
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+            WriteLocationToTrap(trapFile.type_location, this, Location);
         }
 
         public override void WriteId(EscapingTextWriter trapFile)

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs

@@ -81,7 +81,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
 
             // Class location
-            if (!Symbol.IsGenericType || Symbol.IsReallyUnbound())
+            if ((!Symbol.IsGenericType || Symbol.IsReallyUnbound()) && !Context.OnlyScaffold)
             {
                 WriteLocationsToTrap(trapFile.type_location, this, Locations);
             }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/TupleType.cs

@@ -51,6 +51,10 @@ namespace Semmle.Extraction.CSharp.Entities
                     trapFile.tuple_element(this, index++, element);
             }
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
             // Note: symbol.Locations seems to be very inconsistent
             // about what locations are available for a tuple type.
             // Sometimes it's the source code, and sometimes it's empty.

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/Type.cs

@@ -222,7 +222,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         private IEnumerable<BaseTypeSyntax> GetBaseTypeDeclarations()
         {
-            if (!IsSourceDeclaration || !Symbol.FromSource())
+            if (!IsSourceDeclaration || !Symbol.FromSource() || Context.OnlyScaffold)
             {
                 return Enumerable.Empty<BaseTypeSyntax>();
             }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/TypeParameter.cs

@@ -26,6 +26,11 @@ namespace Semmle.Extraction.CSharp.Entities
             var parentNs = Namespace.Create(Context, Symbol.TypeParameterKind == TypeParameterKind.Method ? Context.Compilation.GlobalNamespace : Symbol.ContainingNamespace);
             trapFile.parent_namespace(this, parentNs);
 
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             if (Context.ExtractLocation(Symbol))
             {
                 var locations = Context.GetLocations(Symbol);

csharp/extractor/Semmle.Extraction.CSharp/Entities/UserOperator.cs

@@ -26,6 +26,14 @@ namespace Semmle.Extraction.CSharp.Entities
                 returnType.TypeRef,
                 (UserOperator)OriginalDefinition);
 
+            ContainingType.PopulateGenerics();
+            Overrides(trapFile);
+
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             if (Context.ExtractLocation(Symbol))
             {
                 WriteLocationsToTrap(trapFile.operator_location, this, Locations);
@@ -39,9 +47,6 @@ namespace Semmle.Extraction.CSharp.Entities
                 foreach (var declaration in declSyntaxReferences.OfType<ConversionOperatorDeclarationSyntax>())
                     TypeMention.Create(Context, declaration.Type, this, returnType);
             }
-
-            ContainingType.PopulateGenerics();
-            Overrides(trapFile);
         }
 
         public override bool NeedsPopulation => Context.Defines(Symbol) || IsImplicitOperator(out _);

csharp/extractor/Semmle.Extraction.CSharp/Entities/UsingDirective.cs

@@ -20,6 +20,11 @@ namespace Semmle.Extraction.CSharp.Entities
 
         protected override void Populate(TextWriter trapFile)
         {
+            if (Context.OnlyScaffold)
+            {
+                return;
+            }
+
             // This is guaranteed to be non-null as we only deal with "using namespace" not "using X = Y"
             var name = node.Name!;
 

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Analyser.cs

@@ -41,16 +41,20 @@ namespace Semmle.Extraction.CSharp
 
         public IPathCache PathCache { get; }
 
+        public IOverlayInfo OverlayInfo { get; }
+
         protected Analyser(
             IProgressMonitor pm,
             ILogger logger,
             PathTransformer pathTransformer,
             IPathCache pathCache,
+            IOverlayInfo overlayInfo,
             bool addAssemblyTrapPrefix)
         {
             Logger = logger;
             PathTransformer = pathTransformer;
             PathCache = pathCache;
+            OverlayInfo = overlayInfo;
             this.addAssemblyTrapPrefix = addAssemblyTrapPrefix;
             this.progressMonitor = pm;
 
@@ -158,7 +162,7 @@ namespace Semmle.Extraction.CSharp
 
                     if (compilation.GetAssemblyOrModuleSymbol(r) is IAssemblySymbol assembly)
                     {
-                        var cx = new Context(ExtractionContext, compilation, trapWriter, new AssemblyScope(assembly, assemblyPath), addAssemblyTrapPrefix);
+                        var cx = new Context(ExtractionContext, compilation, trapWriter, new AssemblyScope(assembly, assemblyPath), OverlayInfo, addAssemblyTrapPrefix);
 
                         foreach (var module in assembly.Modules)
                         {
@@ -195,7 +199,7 @@ namespace Semmle.Extraction.CSharp
                 var currentTaskId = IncrementTaskCount();
                 ReportProgressTaskStarted(currentTaskId, sourcePath);
 
-                var cx = new Context(ExtractionContext, compilation, trapWriter, new SourceScope(tree), addAssemblyTrapPrefix);
+                var cx = new Context(ExtractionContext, compilation, trapWriter, new SourceScope(tree), OverlayInfo, addAssemblyTrapPrefix);
                 // Ensure that the file itself is populated in case the source file is totally empty
                 var root = tree.GetRoot();
                 Entities.File.Create(cx, root.SyntaxTree.FilePath);
@@ -234,7 +238,7 @@ namespace Semmle.Extraction.CSharp
                 var assembly = compilation.Assembly;
                 var trapWriter = transformedAssemblyPath.CreateTrapWriter(Logger, options.TrapCompression, discardDuplicates: false);
                 compilationTrapFile = trapWriter;  // Dispose later
-                var cx = new Context(ExtractionContext, compilation, trapWriter, new AssemblyScope(assembly, assemblyPath), addAssemblyTrapPrefix);
+                var cx = new Context(ExtractionContext, compilation, trapWriter, new AssemblyScope(assembly, assemblyPath), OverlayInfo, addAssemblyTrapPrefix);
 
                 compilationEntity = Entities.Compilation.Create(cx);
 

csharp/extractor/Semmle.Extraction.CSharp/Extractor/BinaryLogAnalyser.cs

@@ -8,7 +8,7 @@ namespace Semmle.Extraction.CSharp
     public class BinaryLogAnalyser : Analyser
     {
         public BinaryLogAnalyser(IProgressMonitor pm, ILogger logger, PathTransformer pathTransformer, IPathCache pathCache, bool addAssemblyTrapPrefix)
-            : base(pm, logger, pathTransformer, pathCache, addAssemblyTrapPrefix)
+            : base(pm, logger, pathTransformer, pathCache, new TrivialOverlayInfo(), addAssemblyTrapPrefix)
         {
         }
 

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Context.cs

@@ -29,6 +29,12 @@ namespace Semmle.Extraction.CSharp
         /// </summary>
         public bool ShouldAddAssemblyTrapPrefix { get; }
 
+        /// <summary>
+        /// Holds if trap only should be created for types and member signatures (and not for expressions and statements).
+        /// This is the case for all unchanged files, when running in overlay mode.
+        /// </summary>
+        public bool OnlyScaffold { get; }
+
         public IList<object> TrapStackSuffix { get; } = new List<object>();
 
         private int GetNewId() => TrapWriter.IdCounter++;
@@ -523,13 +529,16 @@ namespace Semmle.Extraction.CSharp
 
         internal CommentProcessor CommentGenerator { get; } = new CommentProcessor();
 
-        public Context(ExtractionContext extractionContext, Compilation c, TrapWriter trapWriter, IExtractionScope scope, bool shouldAddAssemblyTrapPrefix = false)
+        public Context(ExtractionContext extractionContext, Compilation c, TrapWriter trapWriter, IExtractionScope scope, IOverlayInfo overlayInfo, bool shouldAddAssemblyTrapPrefix = false)
         {
             ExtractionContext = extractionContext;
             TrapWriter = trapWriter;
             ShouldAddAssemblyTrapPrefix = shouldAddAssemblyTrapPrefix;
             Compilation = c;
             this.scope = scope;
+            OnlyScaffold = overlayInfo.IsOverlayMode && (
+                IsAssemblyScope
+                || (scope is SourceScope ss && overlayInfo.OnlyMakeScaffold(ss.SourceTree.FilePath)));
         }
 
         public bool FromSource => scope is SourceScope;
@@ -552,7 +561,8 @@ namespace Semmle.Extraction.CSharp
 
         public bool ExtractLocation(ISymbol symbol) =>
             SymbolEqualityComparer.Default.Equals(symbol, symbol.OriginalDefinition) &&
-            scope.InScope(symbol);
+            scope.InScope(symbol) &&
+            !OnlyScaffold;
 
         /// <summary>
         /// Gets the locations of the symbol that are either
@@ -621,6 +631,10 @@ namespace Semmle.Extraction.CSharp
         /// <param name="l">Location of the entity.</param>
         public void BindComments(Entity entity, Microsoft.CodeAnalysis.Location? l)
         {
+            if (OnlyScaffold)
+            {
+                return;
+            }
             var duplicationGuardKey = GetCurrentTagStackKey();
             CommentGenerator.AddElement(entity.Label, duplicationGuardKey, l);
         }

csharp/extractor/Semmle.Extraction.CSharp/Extractor/OverlayInfo.cs

@@ -0,0 +1,124 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.Json;
+using Semmle.Util;
+using Semmle.Util.Logging;
+
+namespace Semmle.Extraction.CSharp
+{
+    public interface IOverlayInfo
+    {
+        /// <summary>
+        /// True, if the extractor is running in overlay mode.
+        /// </summary>
+        bool IsOverlayMode { get; }
+
+        /// <summary>
+        /// Returns true, if the given file is not in the set of changed files.
+        /// </summary>
+        /// <param name="filePath">A source file path</param>
+        bool OnlyMakeScaffold(string filePath);
+    }
+
+
+    /// <summary>
+    /// An instance of this class is used when overlay is not enabled.
+    /// </summary>
+    public class TrivialOverlayInfo : IOverlayInfo
+    {
+        public TrivialOverlayInfo() { }
+
+        public bool IsOverlayMode { get; } = false;
+
+        public bool OnlyMakeScaffold(string filePath) => false;
+    }
+
+    /// <summary>
+    /// An instance of this class is used for detecting
+    /// (1) Whether overlay is enabled.
+    /// (2) Fetch the changed files that should be fully extracted as a part
+    /// of the overlay extraction.
+    /// </summary>
+    public class OverlayInfo : IOverlayInfo
+    {
+        private readonly ILogger logger;
+        private readonly HashSet<string> changedFiles;
+        private readonly string srcDir;
+
+        public OverlayInfo(ILogger logger, string srcDir, string json)
+        {
+            this.logger = logger;
+            this.srcDir = srcDir;
+            changedFiles = ParseJson(json);
+        }
+
+        public bool IsOverlayMode { get; } = true;
+
+        public bool OnlyMakeScaffold(string filePath) => !changedFiles.Contains(filePath);
+
+        /// <summary>
+        /// Private type only used to parse overlay changes JSON files.
+        /// 
+        /// The content of such a file has the format
+        /// {
+        ///  "changes": [
+        ///    "app/controllers/about_controller.xyz",
+        ///    "app/models/about.xyz"
+        ///  ]
+        /// }
+        /// </summary>
+        private record ChangedFiles
+        {
+            public string[]? Changes { get; set; }
+        }
+
+        private HashSet<string> ParseJson(string json)
+        {
+            try
+            {
+                var options = new JsonSerializerOptions { PropertyNameCaseInsensitive = true };
+                var obj = JsonSerializer.Deserialize<ChangedFiles>(json, options);
+                return obj?.Changes is string[] changes
+                    ? changes.Select(change => Path.Join(srcDir, change)).ToHashSet()
+                    : [];
+            }
+            catch (JsonException)
+            {
+                logger.LogError("Overlay: Unable to parse the JSON content from the overlay changes file.");
+                return [];
+            }
+        }
+    }
+
+    public static class OverlayInfoFactory
+    {
+        /// <summary>
+        /// The returned object is used to decide, whether
+        /// (1) The extractor is running in overlay mode.
+        /// (2) Which files to only extract scaffolds for (unchanged files)
+        /// </summary>
+        /// <param name="logger">A logger</param>
+        /// <param name="srcDir">The (overlay) source directory</param>
+        /// <returns>An overlay information object.</returns>
+        public static IOverlayInfo Make(ILogger logger, string srcDir)
+        {
+            if (EnvironmentVariables.GetOverlayChangesFilePath() is string path)
+            {
+                logger.LogInfo($"Overlay: Reading overlay changes from file '{path}'.");
+                try
+                {
+                    var json = File.ReadAllText(path);
+                    return new OverlayInfo(logger, srcDir, json);
+                }
+                catch
+                {
+                    logger.LogError("Overlay: Unexpected error while reading the overlay changes file.");
+                }
+            }
+
+            logger.LogInfo("Overlay: Overlay mode not enabled.");
+            return new TrivialOverlayInfo();
+        }
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Extractor/StandaloneAnalyser.cs

@@ -8,8 +8,8 @@ namespace Semmle.Extraction.CSharp
 {
     public class StandaloneAnalyser : Analyser
     {
-        public StandaloneAnalyser(IProgressMonitor pm, ILogger logger, PathTransformer pathTransformer, IPathCache pathCache, bool addAssemblyTrapPrefix)
+        public StandaloneAnalyser(IProgressMonitor pm, ILogger logger, PathTransformer pathTransformer, IPathCache pathCache, IOverlayInfo overlayInfo, bool addAssemblyTrapPrefix)
-            : base(pm, logger, pathTransformer, pathCache, addAssemblyTrapPrefix)
+            : base(pm, logger, pathTransformer, pathCache, overlayInfo, addAssemblyTrapPrefix)
         {
         }
 

csharp/extractor/Semmle.Extraction.CSharp/Extractor/TracingAnalyser.cs

@@ -14,7 +14,7 @@ namespace Semmle.Extraction.CSharp
         private bool init;
 
         public TracingAnalyser(IProgressMonitor pm, ILogger logger, PathTransformer pathTransformer, IPathCache pathCache, bool addAssemblyTrapPrefix)
-            : base(pm, logger, pathTransformer, pathCache, addAssemblyTrapPrefix)
+            : base(pm, logger, pathTransformer, pathCache, new TrivialOverlayInfo(), addAssemblyTrapPrefix)
         {
         }
 

csharp/extractor/Semmle.Extraction.CSharp/Populators/CommentPopulator.cs

@@ -12,6 +12,10 @@ namespace Semmle.Extraction.CSharp.Populators
     {
         public static void ExtractCommentBlocks(Context cx, CommentProcessor gen)
         {
+            if (cx.OnlyScaffold)
+            {
+                return;
+            }
             cx.Try(null, null, () =>
             {
                 gen.GenerateBindings((entity, duplicationGuardKey, block, binding) =>
@@ -34,6 +38,10 @@ namespace Semmle.Extraction.CSharp.Populators
 
         public static void ExtractComment(Context cx, SyntaxTrivia trivia)
         {
+            if (cx.OnlyScaffold)
+            {
+                return;
+            }
             switch (trivia.Kind())
             {
                 case SyntaxKind.SingleLineDocumentationCommentTrivia:

csharp/extractor/Semmle.Extraction.Tests/OverlayInfo.cs

@@ -0,0 +1,31 @@
+using Xunit;
+using Semmle.Extraction.CSharp;
+using System.IO;
+
+namespace Semmle.Extraction.Tests
+{
+    public class OverlayTests
+    {
+        [Fact]
+        public void TestOverlay()
+        {
+            var logger = new LoggerStub();
+            var json =
+                """
+                {
+                    "changes": [
+                        "app/controllers/about_controller.xyz",
+                        "app/models/about.xyz"
+                    ]
+                }
+                """;
+
+            var overlay = new OverlayInfo(logger, "overlay/source/path", json);
+
+            Assert.True(overlay.IsOverlayMode);
+            Assert.False(overlay.OnlyMakeScaffold("overlay/source/path" + Path.DirectorySeparatorChar + "app/controllers/about_controller.xyz"));
+            Assert.False(overlay.OnlyMakeScaffold("overlay/source/path" + Path.DirectorySeparatorChar + "app/models/about.xyz"));
+            Assert.True(overlay.OnlyMakeScaffold("overlay/source/path" + Path.DirectorySeparatorChar + "app/models/unchanged.xyz"));
+        }
+    }
+}

csharp/extractor/Semmle.Util/EnvironmentVariables.cs

@@ -53,5 +53,28 @@ namespace Semmle.Util
         {
             return Environment.GetEnvironmentVariable(name)?.Split(" ", StringSplitOptions.RemoveEmptyEntries) ?? [];
         }
+
+        /// <summary>
+        /// Used to
+        /// (1) Detect whether the extractor should run in overlay mode.
+        /// (2) Returns the path to the file containing a list of changed files
+        /// in JSON format.
+        ///
+        /// The environment variable is only set in case the extraction is supposed to be
+        /// performed in overlay mode. Furthermore, this only applies to buildless extraction.
+        /// </summary>
+        public static string? GetOverlayChangesFilePath()
+        {
+            return Environment.GetEnvironmentVariable("CODEQL_EXTRACTOR_CSHARP_OVERLAY_CHANGES");
+        }
+
+        /// <summary>
+        /// If the environment variable is set, the extractor is being called to extract a base database.
+        /// Its value will be a path, and the extractor must create either a file or directory at that location.
+        /// </summary>
+        public static string? GetBaseMetaDataOutPath()
+        {
+            return Environment.GetEnvironmentVariable("CODEQL_EXTRACTOR_CSHARP_OVERLAY_BASE_METADATA_OUT");
+        }
     }
 }

csharp/ql/lib/change-notes/2025-10-30-overlay-compilation-and-extraction.md

@@ -0,0 +1,5 @@
+---
+category: feature
+---
+
+* Initial support for incremental C# databases via `codeql database create --overlay-base`/`--overlay-changes`.

csharp/ql/lib/csharp.qll

@@ -36,6 +36,7 @@ import semmle.code.csharp.controlflow.ControlFlowGraph
 import semmle.code.csharp.dataflow.DataFlow
 import semmle.code.csharp.dataflow.TaintTracking
 import semmle.code.csharp.dataflow.SSA
+private import semmle.code.csharp.internal.Overlay
 
 /** Whether the source was extracted without a build command. */
 predicate extractionIsStandalone() { exists(SourceFile f | f.extractedStandalone()) }

csharp/ql/lib/qlpack.yml

@@ -18,3 +18,4 @@ dataExtensions:
   - ext/*.model.yml
   - ext/generated/*.model.yml
 warnOnImplicitThis: true
+compileForOverlayEval: true

csharp/ql/lib/semmle/code/csharp/Conversion.qll

@@ -719,6 +719,15 @@ private Type convTypeParameterBase(TypeParameter tp) {
   result = getATypeParameterFromConstraints+(tp)
 }
 
+pragma[noinline]
+private Class typeConstraintToBaseType(TypeParameterConstraints tpc) {
+  tpc.hasValueTypeConstraint() and result instanceof SystemValueTypeClass
+  or
+  result = tpc.getATypeConstraint()
+  or
+  tpc.hasRefTypeConstraint() and result instanceof ObjectType
+}
+
 /**
  * 10.1.5: Candidates for the effective base class of type parameter `tp`.
  *
@@ -731,13 +740,9 @@ private Class effectiveBaseClassCandidate(TypeParameter tp) {
   not hasPrimaryConstraints(tp) and result instanceof ObjectType
   or
   exists(TypeParameterConstraints tpc | tpc = tp.getConstraints() |
-    tpc.hasValueTypeConstraint() and result instanceof SystemValueTypeClass
+    result = typeConstraintToBaseType(tpc)
-    or
-    result = tpc.getATypeConstraint()
     or
     result = effectiveBaseClassCandidate(tpc.getATypeConstraint())
-    or
-    tpc.hasRefTypeConstraint() and result instanceof ObjectType
   )
 }
 

csharp/ql/lib/semmle/code/csharp/internal/Overlay.qll

@@ -0,0 +1,166 @@
+/**
+ * Defines entity discard predicates for C# overlay analysis.
+ */
+
+/**
+ * Holds always for the overlay variant and never for the base variant.
+ * This local predicate is used to define local predicates that behave
+ * differently for the base and overlay variant.
+ */
+overlay[local]
+predicate isOverlay() { databaseMetadata("isOverlay", "true") }
+
+overlay[local]
+private string getLocationFilePath(@location_default loc) {
+  exists(@file file | locations_default(loc, file, _, _, _, _) | files(file, result))
+}
+
+overlay[local]
+private class DiscardableEntityBase extends @locatable {
+  /** Gets the path to the file in which this element occurs. */
+  abstract string getFilePath();
+
+  /** Holds if this element exists in the base variant. */
+  predicate existsInBase() { not isOverlay() }
+
+  /** Holds if this element exists in the overlay variant. */
+  predicate existsInOverlay() { isOverlay() }
+
+  /** Gets a textual representation of this discardable element. */
+  string toString() { none() }
+}
+
+/**
+ * A class of elements that can be discarded from the base.
+ */
+overlay[local]
+private class DiscardableEntity extends DiscardableEntityBase {
+  /** Gets the path to the file in which this element occurs. */
+  override string getFilePath() {
+    exists(@location_default loc | result = getLocationFilePath(loc) |
+      expr_location(this, loc) or
+      stmt_location(this, loc) or
+      using_directive_location(this, loc) or
+      namespace_declaration_location(this, loc) or
+      preprocessor_directive_location(this, loc) or
+      type_location(this, loc) or
+      attribute_location(this, loc) or
+      type_parameter_constraints_location(this, loc) or
+      property_location(this, loc) or
+      indexer_location(this, loc) or
+      accessor_location(this, loc) or
+      event_location(this, loc) or
+      event_accessor_location(this, loc) or
+      operator_location(this, loc) or
+      method_location(this, loc) or
+      constructor_location(this, loc) or
+      destructor_location(this, loc) or
+      field_location(this, loc) or
+      localvar_location(this, loc) or
+      param_location(this, loc) or
+      type_mention_location(this, loc) or
+      commentline_location(this, loc) or
+      commentblock_location(this, loc) or
+      diagnostics(this, _, _, _, _, loc) or
+      extractor_messages(this, _, _, _, _, loc, _)
+    )
+  }
+}
+
+/**
+ * A class of C# database entities that use `*` IDs.
+ * The rest use named TRAP IDs.
+ */
+overlay[local]
+private class StarEntity =
+  @expr or @stmt or @diagnostic or @extractor_message or @using_directive or @type_mention or
+      @local_variable;
+
+overlay[discard_entity]
+private predicate discardStarEntity(@locatable e) {
+  e instanceof StarEntity and
+  // Entities with *-ids can exist either in base or overlay, but not both.
+  e =
+    any(DiscardableEntity de |
+      overlayChangedFiles(de.getFilePath()) and
+      de.existsInBase()
+    )
+}
+
+overlay[discard_entity]
+private predicate discardNamedEntity(@locatable e) {
+  not e instanceof StarEntity and
+  // Entities with named IDs can exist both in base, overlay, or both.
+  e =
+    any(DiscardableEntity de |
+      overlayChangedFiles(de.getFilePath()) and
+      not de.existsInOverlay()
+    )
+}
+
+overlay[local]
+private predicate discardableLocation(@location_default loc, string path) {
+  not isOverlay() and
+  path = getLocationFilePath(loc)
+}
+
+// Discard locations that are in changed files from the base variant.
+overlay[discard_entity]
+private predicate discardLocation(@location_default loc) {
+  exists(string path | discardableLocation(loc, path) | overlayChangedFiles(path))
+}
+
+/**
+ * A class of Xml locatables that can be discarded from the base.
+ */
+overlay[local]
+private class DiscardableXmlEntity extends DiscardableEntityBase instanceof @xmllocatable {
+  /** Gets the path to the file in which this element occurs. */
+  override string getFilePath() {
+    exists(@location_default loc | result = getLocationFilePath(loc) | xmllocations(this, loc))
+  }
+}
+
+overlay[local]
+private predicate overlayXmlExtracted(string file) {
+  exists(DiscardableXmlEntity dxe |
+    dxe.existsInOverlay() and
+    file = dxe.getFilePath() and
+    not files(dxe, _) and
+    not xmlNs(dxe, _, _, _)
+  )
+}
+
+overlay[discard_entity]
+private predicate discardXmlEntity(@xmllocatable xml) {
+  overlayChangedFiles(xml.(DiscardableXmlEntity).getFilePath())
+  or
+  // The XML extractor is not incremental and may extract more
+  // XML files than those included in overlayChangedFiles.
+  overlayXmlExtracted(xml.(DiscardableXmlEntity).getFilePath())
+}
+
+overlay[local]
+private class DiscardableAspEntity extends DiscardableEntityBase instanceof @asp_element {
+  /** Gets the path to the file in which this element occurs. */
+  override string getFilePath() {
+    exists(@location_default loc | result = getLocationFilePath(loc) | asp_elements(this, _, loc))
+  }
+}
+
+overlay[local]
+private predicate overlayAspExtracted(string file) {
+  exists(DiscardableAspEntity dae |
+    dae.existsInOverlay() and
+    file = dae.getFilePath()
+  )
+}
+
+overlay[discard_entity]
+private predicate discardAspEntity(@asp_element asp) {
+  overlayChangedFiles(asp.(DiscardableAspEntity).getFilePath())
+  or
+  // The ASP extractor is not incremental and may extract more
+  // ASP files than those included in overlayChangedFiles.
+  overlayAspExtracted(asp.(DiscardableAspEntity).getFilePath())
+}

csharp/ql/lib/semmlecode.csharp.dbscheme

@@ -194,6 +194,24 @@ externalData(
 sourceLocationPrefix(
   string prefix: string ref);
 
+/*
+ * Overlay support
+ */
+
+/**
+ * The CLI will automatically emit the tuple `databaseMetadata("isOverlay", "true")`,
+ * along with an `overlayChangedFiles` tuple for each new/modified/deleted file,
+ * when building an overlay database, and these can be used by the discard predicates.
+ */
+databaseMetadata(
+  string metadataKey : string ref,
+  string value : string ref
+);
+
+overlayChangedFiles(
+  string path : string ref
+);
+
 /*
  * C# dbscheme
  */
@@ -222,6 +240,12 @@ sourceLocationPrefix(
 
 @location = @location_default | @assembly;
 
+@locatable = @declaration_with_accessors | @callable_accessor | @declaration_or_directive
+           | @diagnostic | @extractor_message | @preprocessor_directive | @attribute | @type_mention | @type_parameter_constraints
+           | @declaration_with_accessors | @callable_accessor | @operator | @method
+           | @constructor | @destructor | @field | @local_variable | @parameter | @stmt | @expr
+           | @xmllocatable | @commentline | @commentblock | @asp_element
+
 locations_default(
   unique int id: @location_default,
   int file: @file ref,

csharp/ql/lib/upgrades/605f85053409cd72b4904df3f198ddc8324f3a83/upgrade.properties

@@ -0,0 +1,2 @@
+description: Add @locatable type
+compatibility: full

csharp/ql/lib/upgrades/66044cfa5bbf2ecfabd06ead25e91db2bdd79764/upgrade.properties

@@ -0,0 +1,2 @@
+description: Add databaseMetadata and overlayChangedFiles relations
+compatibility: full

csharp/ql/test/library-tests/csharp11/PrintAst.expected

@@ -1234,9 +1234,9 @@ StaticInterfaceMembers.cs:
 #   49|       1: [PropertyCall] access to property Real
 #   49|         -1: [ParameterAccess] access to parameter n
 #   51|   14: [Method] Inc
-#   51|     -1: [TypeMention] Complex
 #   51|     -1: [TypeMention] INumber<Complex>
 #   51|       1: [TypeMention] Complex
+#   51|     -1: [TypeMention] Complex
 #-----|     2: (Parameters)
 #   51|       0: [Parameter] other
 #   51|         -1: [TypeMention] Complex
@@ -1254,9 +1254,9 @@ StaticInterfaceMembers.cs:
 #   52|           1: [PropertyCall] access to property Imaginary
 #   52|             -1: [ParameterAccess] access to parameter other
 #   54|   15: [Method] Dec
-#   54|     -1: [TypeMention] Complex
 #   54|     -1: [TypeMention] INumber<Complex>
 #   54|       1: [TypeMention] Complex
+#   54|     -1: [TypeMention] Complex
 #-----|     2: (Parameters)
 #   54|       0: [Parameter] other
 #   54|         -1: [TypeMention] Complex

csharp/ql/test/library-tests/definitions/PrintAst.expected

@@ -272,8 +272,8 @@ definitions.cs:
 #  125|           0: [MethodCall] call to method M
 #  125|             -1: [BaseAccess] base access
 #  128|     6: [Method] M2`1
-#  128|       -1: [TypeMention] Void
 #  128|       -1: [TypeMention] I1
+#  128|       -1: [TypeMention] Void
 #-----|       1: (Type parameters)
 #  128|         0: [TypeParameter] T
 #  128|       4: [BlockStmt] {...}
@@ -356,8 +356,8 @@ definitions.cs:
 #  153|           0: [Parameter] value
 #  153|         4: [BlockStmt] {...}
 #  154|     6: [Method] M
-#  154|       -1: [TypeMention] A
 #  154|       -1: [TypeMention] I4
+#  154|       -1: [TypeMention] A
 #  154|       4: [ThrowExpr] throw ...
 #  154|         0: [ObjectCreation] object creation of type Exception
 #  154|           0: [TypeMention] Exception

csharp/ql/test/library-tests/overlay/base/A.cs

@@ -0,0 +1,66 @@
+using System;
+
+namespace ConsoleApp1
+{
+    public class A
+    {
+        private string name;
+        public A(string x)
+        {
+            name = x;
+        }
+
+        // Destructor
+        ~A()
+        {
+            Console.WriteLine("Destructor called!");
+        }
+
+        public string Prop { get; set; } = "Hello";
+
+        public object this[int i]
+        {
+            get { return new object(); }
+            set { }
+        }
+
+        /*
+         * An example event
+         */
+        public event EventHandler Clicked
+        {
+            add
+            {
+                Console.WriteLine("Handler added");
+            }
+            remove
+            {
+                Console.WriteLine("Handler removed");
+            }
+        }
+
+        public static A operator +(A a, A b)
+        {
+            return a;
+        }
+
+        [MyObsolete]
+        public void ObsoleteMethod() { }
+
+        public int OldMethod(int x)
+        {
+            var y = x + 1;
+            return y;
+        }
+
+        public override string ToString()
+        {
+            var x = $"A: {name}";
+            return x;
+        }
+    }
+
+    public class MyObsoleteAttribute : Attribute { }
+
+    public class B { }
+}

csharp/ql/test/library-tests/overlay/base/Program.cs

@@ -0,0 +1,65 @@
+using System;
+
+namespace ConsoleApp1
+{
+    internal class Program
+    {
+        public static void Main(string[] args)
+        {
+            if (args.Length == 0)
+            {
+                Console.WriteLine("Print usage instructions here.");
+                return;
+            }
+            var x = args[0];
+            var a = new A(x);
+            Console.WriteLine(a.ToString());
+        }
+
+        private string programName;
+
+        public Program(string x)
+        {
+            programName = x;
+        }
+
+        // Program destructor
+        ~Program()
+        {
+            Console.WriteLine("Program destructor called!");
+        }
+
+        public string ProgramProp { get; set; } = "Hello World!";
+
+        public string this[int i]
+        {
+            get { return string.Empty; }
+            set { }
+        }
+
+        /*
+         * A program event.
+         */
+        public event EventHandler ProgramClicked
+        {
+            add
+            {
+                Console.WriteLine("Program handler added");
+            }
+            remove
+            {
+                Console.WriteLine("Program handler removed");
+            }
+        }
+
+        public static Program operator -(Program a, Program b)
+        {
+            return b;
+        }
+
+        [Program]
+        public void AnnotatedMethod() { }
+    }
+
+    public class ProgramAttribute : Attribute { }
+}

csharp/ql/test/library-tests/overlay/base/options

@@ -0,0 +1 @@
+semmle-extractor-options: --standalone

csharp/ql/test/library-tests/overlay/base/test.expected

@@ -0,0 +1,276 @@
+expressions
+| A.cs:8:16:8:16 | call to constructor Object |
+| A.cs:10:13:10:16 | access to field name |
+| A.cs:10:13:10:16 | this access |
+| A.cs:10:13:10:20 | ... = ... |
+| A.cs:10:20:10:20 | access to parameter x |
+| A.cs:16:13:16:19 | access to type Console |
+| A.cs:16:13:16:51 | call to method WriteLine |
+| A.cs:16:31:16:50 | "Destructor called!" |
+| A.cs:19:23:19:26 | access to property Prop |
+| A.cs:19:23:19:26 | this access |
+| A.cs:19:42:19:50 | ... = ... |
+| A.cs:19:44:19:50 | "Hello" |
+| A.cs:23:26:23:37 | object creation of type Object |
+| A.cs:34:17:34:23 | access to type Console |
+| A.cs:34:17:34:50 | call to method WriteLine |
+| A.cs:34:35:34:49 | "Handler added" |
+| A.cs:38:17:38:23 | access to type Console |
+| A.cs:38:17:38:52 | call to method WriteLine |
+| A.cs:38:35:38:51 | "Handler removed" |
+| A.cs:44:20:44:20 | access to parameter a |
+| A.cs:52:17:52:17 | access to local variable y |
+| A.cs:52:17:52:25 | Int32 y = ... |
+| A.cs:52:21:52:21 | access to parameter x |
+| A.cs:52:21:52:25 | ... + ... |
+| A.cs:52:25:52:25 | 1 |
+| A.cs:53:20:53:20 | access to local variable y |
+| A.cs:58:17:58:17 | access to local variable x |
+| A.cs:58:17:58:32 | String x = ... |
+| A.cs:58:21:58:32 | $"..." |
+| A.cs:58:23:58:25 | "A: " |
+| A.cs:58:26:58:31 | {...} |
+| A.cs:58:27:58:30 | access to field name |
+| A.cs:58:27:58:30 | this access |
+| A.cs:59:20:59:20 | access to local variable x |
+| A.cs:63:18:63:36 | call to constructor Attribute |
+| A.cs:65:18:65:18 | call to constructor Object |
+| Program.cs:9:17:9:20 | access to parameter args |
+| Program.cs:9:17:9:27 | access to property Length |
+| Program.cs:9:17:9:32 | ... == ... |
+| Program.cs:9:32:9:32 | 0 |
+| Program.cs:11:17:11:23 | access to type Console |
+| Program.cs:11:17:11:67 | call to method WriteLine |
+| Program.cs:11:35:11:66 | "Print usage instructions here." |
+| Program.cs:14:17:14:17 | access to local variable x |
+| Program.cs:14:17:14:27 | String x = ... |
+| Program.cs:14:21:14:24 | access to parameter args |
+| Program.cs:14:21:14:27 | access to array element |
+| Program.cs:14:26:14:26 | 0 |
+| Program.cs:15:17:15:17 | access to local variable a |
+| Program.cs:15:17:15:28 | A a = ... |
+| Program.cs:15:21:15:28 | object creation of type A |
+| Program.cs:15:27:15:27 | access to local variable x |
+| Program.cs:16:13:16:19 | access to type Console |
+| Program.cs:16:13:16:43 | call to method WriteLine |
+| Program.cs:16:31:16:31 | access to local variable a |
+| Program.cs:16:31:16:42 | call to method ToString |
+| Program.cs:21:16:21:22 | call to constructor Object |
+| Program.cs:23:13:23:23 | access to field programName |
+| Program.cs:23:13:23:23 | this access |
+| Program.cs:23:13:23:27 | ... = ... |
+| Program.cs:23:27:23:27 | access to parameter x |
+| Program.cs:29:13:29:19 | access to type Console |
+| Program.cs:29:13:29:59 | call to method WriteLine |
+| Program.cs:29:31:29:58 | "Program destructor called!" |
+| Program.cs:32:23:32:33 | access to property ProgramProp |
+| Program.cs:32:23:32:33 | this access |
+| Program.cs:32:49:32:64 | ... = ... |
+| Program.cs:32:51:32:64 | "Hello World!" |
+| Program.cs:36:26:36:31 | access to type String |
+| Program.cs:36:26:36:37 | access to field Empty |
+| Program.cs:47:17:47:23 | access to type Console |
+| Program.cs:47:17:47:58 | call to method WriteLine |
+| Program.cs:47:35:47:57 | "Program handler added" |
+| Program.cs:51:17:51:23 | access to type Console |
+| Program.cs:51:17:51:60 | call to method WriteLine |
+| Program.cs:51:35:51:59 | "Program handler removed" |
+| Program.cs:57:20:57:20 | access to parameter b |
+| Program.cs:64:18:64:33 | call to constructor Attribute |
+statements
+| A.cs:9:9:11:9 | {...} |
+| A.cs:10:13:10:21 | ...; |
+| A.cs:15:9:17:9 | {...} |
+| A.cs:16:13:16:52 | ...; |
+| A.cs:23:17:23:40 | {...} |
+| A.cs:23:19:23:38 | return ...; |
+| A.cs:24:17:24:19 | {...} |
+| A.cs:33:13:35:13 | {...} |
+| A.cs:34:17:34:51 | ...; |
+| A.cs:37:13:39:13 | {...} |
+| A.cs:38:17:38:53 | ...; |
+| A.cs:43:9:45:9 | {...} |
+| A.cs:44:13:44:21 | return ...; |
+| A.cs:48:38:48:40 | {...} |
+| A.cs:51:9:54:9 | {...} |
+| A.cs:52:13:52:26 | ... ...; |
+| A.cs:53:13:53:21 | return ...; |
+| A.cs:57:9:60:9 | {...} |
+| A.cs:58:13:58:33 | ... ...; |
+| A.cs:59:13:59:21 | return ...; |
+| A.cs:63:18:63:36 | {...} |
+| A.cs:65:18:65:18 | {...} |
+| Program.cs:8:9:17:9 | {...} |
+| Program.cs:9:13:13:13 | if (...) ... |
+| Program.cs:10:13:13:13 | {...} |
+| Program.cs:11:17:11:68 | ...; |
+| Program.cs:12:17:12:23 | return ...; |
+| Program.cs:14:13:14:28 | ... ...; |
+| Program.cs:15:13:15:29 | ... ...; |
+| Program.cs:16:13:16:44 | ...; |
+| Program.cs:22:9:24:9 | {...} |
+| Program.cs:23:13:23:28 | ...; |
+| Program.cs:28:9:30:9 | {...} |
+| Program.cs:29:13:29:60 | ...; |
+| Program.cs:36:17:36:40 | {...} |
+| Program.cs:36:19:36:38 | return ...; |
+| Program.cs:37:17:37:19 | {...} |
+| Program.cs:46:13:48:13 | {...} |
+| Program.cs:47:17:47:59 | ...; |
+| Program.cs:50:13:52:13 | {...} |
+| Program.cs:51:17:51:61 | ...; |
+| Program.cs:56:9:58:9 | {...} |
+| Program.cs:57:13:57:21 | return ...; |
+| Program.cs:61:39:61:41 | {...} |
+| Program.cs:64:18:64:33 | {...} |
+methods
+| A.cs:48:21:48:34 | ObsoleteMethod |
+| A.cs:50:20:50:28 | OldMethod |
+| A.cs:56:32:56:39 | ToString |
+| Program.cs:7:28:7:31 | Main |
+| Program.cs:61:21:61:35 | AnnotatedMethod |
+types
+| A.cs:5:18:5:18 | A |
+| A.cs:63:18:63:36 | MyObsoleteAttribute |
+| A.cs:65:18:65:18 | B |
+| Program.cs:5:20:5:26 | Program |
+| Program.cs:64:18:64:33 | ProgramAttribute |
+parameters
+| A.cs:8:25:8:25 | x |
+| A.cs:19:35:19:37 | value |
+| A.cs:21:32:21:32 | i |
+| A.cs:21:32:21:32 | i |
+| A.cs:21:32:21:32 | i |
+| A.cs:24:13:24:15 | value |
+| A.cs:32:13:32:15 | value |
+| A.cs:36:13:36:18 | value |
+| A.cs:42:38:42:38 | a |
+| A.cs:42:43:42:43 | b |
+| A.cs:50:34:50:34 | x |
+| Program.cs:7:42:7:45 | args |
+| Program.cs:21:31:21:31 | x |
+| Program.cs:32:42:32:44 | value |
+| Program.cs:34:32:34:32 | i |
+| Program.cs:34:32:34:32 | i |
+| Program.cs:34:32:34:32 | i |
+| Program.cs:37:13:37:15 | value |
+| Program.cs:45:13:45:15 | value |
+| Program.cs:49:13:49:18 | value |
+| Program.cs:55:50:55:50 | a |
+| Program.cs:55:61:55:61 | b |
+operators
+| A.cs:42:34:42:34 | + |
+| Program.cs:55:40:55:40 | - |
+constructors
+| A.cs:8:16:8:16 | A |
+| Program.cs:21:16:21:22 | Program |
+destructors
+| A.cs:14:10:14:10 | ~A |
+| Program.cs:27:10:27:16 | ~Program |
+fields
+| A.cs:7:24:7:27 | name |
+| Program.cs:19:24:19:34 | programName |
+properties
+| A.cs:19:23:19:26 | Prop |
+| Program.cs:32:23:32:33 | ProgramProp |
+indexers
+| A.cs:21:23:21:26 | Item |
+| Program.cs:34:23:34:26 | Item |
+accessors
+| A.cs:19:30:19:32 | get_Prop |
+| A.cs:19:35:19:37 | set_Prop |
+| A.cs:23:13:23:15 | get_Item |
+| A.cs:24:13:24:15 | set_Item |
+| A.cs:32:13:32:15 | add_Clicked |
+| A.cs:36:13:36:18 | remove_Clicked |
+| Program.cs:32:37:32:39 | get_ProgramProp |
+| Program.cs:32:42:32:44 | set_ProgramProp |
+| Program.cs:36:13:36:15 | get_Item |
+| Program.cs:37:13:37:15 | set_Item |
+| Program.cs:45:13:45:15 | add_ProgramClicked |
+| Program.cs:49:13:49:18 | remove_ProgramClicked |
+attributes
+| A.cs:47:10:47:19 | [MyObsolete(...)] |
+| Program.cs:60:10:60:16 | [Program(...)] |
+events
+| A.cs:30:35:30:41 | Clicked |
+| Program.cs:43:35:43:48 | ProgramClicked |
+eventAccessors
+| A.cs:32:13:32:15 | add_Clicked |
+| A.cs:36:13:36:18 | remove_Clicked |
+| Program.cs:45:13:45:15 | add_ProgramClicked |
+| Program.cs:49:13:49:18 | remove_ProgramClicked |
+usingDirectives
+| A.cs:1:1:1:13 | using ...; |
+| Program.cs:1:1:1:13 | using ...; |
+commentLines
+| A.cs:13:9:13:21 | // ... |
+| A.cs:27:9:27:10 | /* ... */ |
+| A.cs:28:1:28:27 | /* ... */ |
+| A.cs:29:1:29:11 | /* ... */ |
+| Program.cs:26:9:26:29 | // ... |
+| Program.cs:40:9:40:10 | /* ... */ |
+| Program.cs:41:1:41:27 | /* ... */ |
+| Program.cs:42:1:42:11 | /* ... */ |
+commentBlocks
+| A.cs:13:9:13:21 | // ... |
+| A.cs:27:9:29:11 | /* ... */ |
+| Program.cs:26:9:26:29 | // ... |
+| Program.cs:40:9:42:11 | /* ... */ |
+typeMentions
+| A.cs:7:17:7:22 | String |
+| A.cs:8:18:8:23 | String |
+| A.cs:16:13:16:19 | Console |
+| A.cs:19:16:19:21 | String |
+| A.cs:21:16:21:21 | Object |
+| A.cs:21:28:21:30 | Int32 |
+| A.cs:23:30:23:35 | Object |
+| A.cs:34:17:34:23 | Console |
+| A.cs:38:17:38:23 | Console |
+| A.cs:42:23:42:23 | A |
+| A.cs:42:36:42:36 | A |
+| A.cs:42:41:42:41 | A |
+| A.cs:47:10:47:19 | MyObsoleteAttribute |
+| A.cs:48:16:48:19 | Void |
+| A.cs:50:16:50:18 | Int32 |
+| A.cs:50:30:50:32 | Int32 |
+| A.cs:52:13:52:15 | Int32 |
+| A.cs:56:25:56:30 | String |
+| A.cs:58:13:58:15 | String |
+| A.cs:63:40:63:48 | Attribute |
+| Program.cs:7:23:7:26 | Void |
+| Program.cs:7:33:7:38 | String |
+| Program.cs:7:33:7:40 | String[] |
+| Program.cs:11:17:11:23 | Console |
+| Program.cs:14:13:14:15 | String |
+| Program.cs:15:13:15:15 | A |
+| Program.cs:15:25:15:25 | A |
+| Program.cs:16:13:16:19 | Console |
+| Program.cs:19:17:19:22 | String |
+| Program.cs:21:24:21:29 | String |
+| Program.cs:29:13:29:19 | Console |
+| Program.cs:32:16:32:21 | String |
+| Program.cs:34:16:34:21 | String |
+| Program.cs:34:28:34:30 | Int32 |
+| Program.cs:36:26:36:31 | String |
+| Program.cs:47:17:47:23 | Console |
+| Program.cs:51:17:51:23 | Console |
+| Program.cs:55:23:55:29 | Program |
+| Program.cs:55:42:55:48 | Program |
+| Program.cs:55:53:55:59 | Program |
+| Program.cs:60:10:60:16 | ProgramAttribute |
+| Program.cs:61:16:61:19 | Void |
+| Program.cs:64:37:64:45 | Attribute |
+xmlLocatables
+| web.changed.config:2:1:12:17 | configuration |
+| web.changed.config:3:3:4:16 | system.web |
+| web.changed.config:5:3:11:22 | system.webServer |
+| web.changed.config:6:5:10:20 | httpProtocol |
+| web.changed.config:7:7:9:23 | customHeaders |
+| web.changed.config:8:9:8:42 | add |
+| web.changed.config:8:9:8:42 | name=MyOption |
+| web.changed.config:8:9:8:42 | value=1 |
+| web.unchanged.config:2:1:6:17 | configuration |
+| web.unchanged.config:3:3:5:16 | system.web |
+| web.unchanged.config:4:5:4:37 | httpCookies |
+| web.unchanged.config:4:5:4:37 | requireSSL=true |

csharp/ql/test/library-tests/overlay/base/test.qlref

@@ -0,0 +1 @@
+query: ../test.ql

csharp/ql/test/library-tests/overlay/base/web.changed.config

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+  <system.web>
+  </system.web>
+  <system.webServer>
+    <httpProtocol>
+      <customHeaders>
+        <add name="MyOption" value="1" />
+      </customHeaders>
+    </httpProtocol>
+  </system.webServer>
+</configuration>

csharp/ql/test/library-tests/overlay/base/web.unchanged.config

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+  <system.web>
+    <httpCookies requireSSL="true"/>
+  </system.web>
+</configuration>

csharp/ql/test/library-tests/overlay/codeql-test.yml

@@ -0,0 +1,3 @@
+overlay:
+  base: "base/"
+  overlay: "overlay/"

csharp/ql/test/library-tests/overlay/options

@@ -0,0 +1 @@
+semmle-extractor-options: --standalone

csharp/ql/test/library-tests/overlay/overlay/A.cs

@@ -0,0 +1,70 @@
+using System;
+
+namespace ConsoleApp1
+{
+    public class C { }
+
+    public class A
+    {
+        private string name;
+        public A(string x)
+        {
+            name = x;
+        }
+
+        // Destructor
+        ~A()
+        {
+            Console.WriteLine("Destructor called!");
+        }
+
+        public string Prop { get; set; } = "Hello";
+
+        public object this[int i]
+        {
+            get { return new object(); }
+            set { }
+        }
+
+        /*
+         * An example event
+         */
+        public event EventHandler Clicked
+        {
+            add
+            {
+                Console.WriteLine("Handler added");
+            }
+            remove
+            {
+                Console.WriteLine("Handler removed");
+            }
+        }
+
+        public static A operator +(A a, A b)
+        {
+            return a;
+        }
+
+        [MyObsolete]
+        public void ObsoleteMethod() { }
+
+
+        public override string ToString()
+        {
+            string y;
+            y = $"Name: {name}";
+            return y;
+        }
+
+        public void NewMethod()
+        {
+            if (name.EndsWith("test"))
+            {
+                name = name.ToUpper();
+            }
+        }
+    }
+
+    public class MyObsoleteAttribute : Attribute { }
+}

csharp/ql/test/library-tests/overlay/overlay/Program.cs

@@ -0,0 +1,65 @@
+using System;
+
+namespace ConsoleApp1
+{
+    internal class Program
+    {
+        public static void Main(string[] args)
+        {
+            if (args.Length == 0)
+            {
+                Console.WriteLine("Print usage instructions here.");
+                return;
+            }
+            var x = args[0];
+            var a = new A(x);
+            Console.WriteLine(a.ToString());
+        }
+
+        private string programName;
+
+        public Program(string x)
+        {
+            programName = x;
+        }
+
+        // Program destructor
+        ~Program()
+        {
+            Console.WriteLine("Program destructor called!");
+        }
+
+        public string ProgramProp { get; set; } = "Hello World!";
+
+        public string this[int i]
+        {
+            get { return string.Empty; }
+            set { }
+        }
+
+        /*
+         * A program event.
+         */
+        public event EventHandler ProgramClicked
+        {
+            add
+            {
+                Console.WriteLine("Program handler added");
+            }
+            remove
+            {
+                Console.WriteLine("Program handler removed");
+            }
+        }
+
+        public static Program operator -(Program a, Program b)
+        {
+            return b;
+        }
+
+        [Program]
+        public void AnnotatedMethod() { }
+    }
+
+    public class ProgramAttribute : Attribute { }
+}

csharp/ql/test/library-tests/overlay/overlay/options

@@ -0,0 +1 @@
+semmle-extractor-options: --standalone

csharp/ql/test/library-tests/overlay/overlay/test.expected

@@ -0,0 +1,274 @@
+expressions
+| A.cs:5:18:5:18 | call to constructor Object |
+| A.cs:10:16:10:16 | call to constructor Object |
+| A.cs:12:13:12:16 | access to field name |
+| A.cs:12:13:12:16 | this access |
+| A.cs:12:13:12:20 | ... = ... |
+| A.cs:12:20:12:20 | access to parameter x |
+| A.cs:18:13:18:19 | access to type Console |
+| A.cs:18:13:18:51 | call to method WriteLine |
+| A.cs:18:31:18:50 | "Destructor called!" |
+| A.cs:21:23:21:26 | access to property Prop |
+| A.cs:21:23:21:26 | this access |
+| A.cs:21:42:21:50 | ... = ... |
+| A.cs:21:44:21:50 | "Hello" |
+| A.cs:25:26:25:37 | object creation of type Object |
+| A.cs:36:17:36:23 | access to type Console |
+| A.cs:36:17:36:50 | call to method WriteLine |
+| A.cs:36:35:36:49 | "Handler added" |
+| A.cs:40:17:40:23 | access to type Console |
+| A.cs:40:17:40:52 | call to method WriteLine |
+| A.cs:40:35:40:51 | "Handler removed" |
+| A.cs:46:20:46:20 | access to parameter a |
+| A.cs:55:20:55:20 | String y |
+| A.cs:56:13:56:13 | access to local variable y |
+| A.cs:56:13:56:31 | ... = ... |
+| A.cs:56:17:56:31 | $"..." |
+| A.cs:56:19:56:24 | "Name: " |
+| A.cs:56:25:56:30 | {...} |
+| A.cs:56:26:56:29 | access to field name |
+| A.cs:56:26:56:29 | this access |
+| A.cs:57:20:57:20 | access to local variable y |
+| A.cs:62:17:62:20 | access to field name |
+| A.cs:62:17:62:20 | this access |
+| A.cs:62:17:62:37 | call to method EndsWith |
+| A.cs:62:31:62:36 | "test" |
+| A.cs:64:17:64:20 | access to field name |
+| A.cs:64:17:64:20 | this access |
+| A.cs:64:17:64:37 | ... = ... |
+| A.cs:64:24:64:27 | access to field name |
+| A.cs:64:24:64:27 | this access |
+| A.cs:64:24:64:37 | call to method ToUpper |
+| A.cs:69:18:69:36 | call to constructor Attribute |
+| Program.cs:9:17:9:20 | access to parameter args |
+| Program.cs:9:17:9:27 | access to property Length |
+| Program.cs:9:17:9:32 | ... == ... |
+| Program.cs:9:32:9:32 | 0 |
+| Program.cs:11:17:11:23 | access to type Console |
+| Program.cs:11:17:11:67 | call to method WriteLine |
+| Program.cs:11:35:11:66 | "Print usage instructions here." |
+| Program.cs:14:17:14:17 | access to local variable x |
+| Program.cs:14:17:14:27 | String x = ... |
+| Program.cs:14:21:14:24 | access to parameter args |
+| Program.cs:14:21:14:27 | access to array element |
+| Program.cs:14:26:14:26 | 0 |
+| Program.cs:15:17:15:17 | access to local variable a |
+| Program.cs:15:17:15:28 | A a = ... |
+| Program.cs:15:21:15:28 | object creation of type A |
+| Program.cs:15:27:15:27 | access to local variable x |
+| Program.cs:16:13:16:19 | access to type Console |
+| Program.cs:16:13:16:43 | call to method WriteLine |
+| Program.cs:16:31:16:31 | access to local variable a |
+| Program.cs:16:31:16:42 | call to method ToString |
+| Program.cs:21:16:21:22 | call to constructor Object |
+| Program.cs:23:13:23:23 | access to field programName |
+| Program.cs:23:13:23:23 | this access |
+| Program.cs:23:13:23:27 | ... = ... |
+| Program.cs:23:27:23:27 | access to parameter x |
+| Program.cs:29:13:29:19 | access to type Console |
+| Program.cs:29:13:29:59 | call to method WriteLine |
+| Program.cs:29:31:29:58 | "Program destructor called!" |
+| Program.cs:32:23:32:33 | access to property ProgramProp |
+| Program.cs:32:23:32:33 | this access |
+| Program.cs:32:49:32:64 | ... = ... |
+| Program.cs:32:51:32:64 | "Hello World!" |
+| Program.cs:36:26:36:31 | access to type String |
+| Program.cs:36:26:36:37 | access to field Empty |
+| Program.cs:47:17:47:23 | access to type Console |
+| Program.cs:47:17:47:58 | call to method WriteLine |
+| Program.cs:47:35:47:57 | "Program handler added" |
+| Program.cs:51:17:51:23 | access to type Console |
+| Program.cs:51:17:51:60 | call to method WriteLine |
+| Program.cs:51:35:51:59 | "Program handler removed" |
+| Program.cs:57:20:57:20 | access to parameter b |
+| Program.cs:64:18:64:33 | call to constructor Attribute |
+statements
+| A.cs:5:18:5:18 | {...} |
+| A.cs:11:9:13:9 | {...} |
+| A.cs:12:13:12:21 | ...; |
+| A.cs:17:9:19:9 | {...} |
+| A.cs:18:13:18:52 | ...; |
+| A.cs:25:17:25:40 | {...} |
+| A.cs:25:19:25:38 | return ...; |
+| A.cs:26:17:26:19 | {...} |
+| A.cs:35:13:37:13 | {...} |
+| A.cs:36:17:36:51 | ...; |
+| A.cs:39:13:41:13 | {...} |
+| A.cs:40:17:40:53 | ...; |
+| A.cs:45:9:47:9 | {...} |
+| A.cs:46:13:46:21 | return ...; |
+| A.cs:50:38:50:40 | {...} |
+| A.cs:54:9:58:9 | {...} |
+| A.cs:55:13:55:21 | ... ...; |
+| A.cs:56:13:56:32 | ...; |
+| A.cs:57:13:57:21 | return ...; |
+| A.cs:61:9:66:9 | {...} |
+| A.cs:62:13:65:13 | if (...) ... |
+| A.cs:63:13:65:13 | {...} |
+| A.cs:64:17:64:38 | ...; |
+| A.cs:69:18:69:36 | {...} |
+| Program.cs:8:9:17:9 | {...} |
+| Program.cs:9:13:13:13 | if (...) ... |
+| Program.cs:10:13:13:13 | {...} |
+| Program.cs:11:17:11:68 | ...; |
+| Program.cs:12:17:12:23 | return ...; |
+| Program.cs:14:13:14:28 | ... ...; |
+| Program.cs:15:13:15:29 | ... ...; |
+| Program.cs:16:13:16:44 | ...; |
+| Program.cs:22:9:24:9 | {...} |
+| Program.cs:23:13:23:28 | ...; |
+| Program.cs:28:9:30:9 | {...} |
+| Program.cs:29:13:29:60 | ...; |
+| Program.cs:36:17:36:40 | {...} |
+| Program.cs:36:19:36:38 | return ...; |
+| Program.cs:37:17:37:19 | {...} |
+| Program.cs:46:13:48:13 | {...} |
+| Program.cs:47:17:47:59 | ...; |
+| Program.cs:50:13:52:13 | {...} |
+| Program.cs:51:17:51:61 | ...; |
+| Program.cs:56:9:58:9 | {...} |
+| Program.cs:57:13:57:21 | return ...; |
+| Program.cs:61:39:61:41 | {...} |
+| Program.cs:64:18:64:33 | {...} |
+methods
+| A.cs:50:21:50:34 | ObsoleteMethod |
+| A.cs:53:32:53:39 | ToString |
+| A.cs:60:21:60:29 | NewMethod |
+| Program.cs:7:28:7:31 | Main |
+| Program.cs:61:21:61:35 | AnnotatedMethod |
+types
+| A.cs:5:18:5:18 | C |
+| A.cs:7:18:7:18 | A |
+| A.cs:69:18:69:36 | MyObsoleteAttribute |
+| Program.cs:5:20:5:26 | Program |
+| Program.cs:64:18:64:33 | ProgramAttribute |
+parameters
+| A.cs:10:25:10:25 | x |
+| A.cs:21:35:21:37 | value |
+| A.cs:23:32:23:32 | i |
+| A.cs:23:32:23:32 | i |
+| A.cs:23:32:23:32 | i |
+| A.cs:26:13:26:15 | value |
+| A.cs:34:13:34:15 | value |
+| A.cs:38:13:38:18 | value |
+| A.cs:44:38:44:38 | a |
+| A.cs:44:43:44:43 | b |
+| Program.cs:7:42:7:45 | args |
+| Program.cs:21:31:21:31 | x |
+| Program.cs:32:42:32:44 | value |
+| Program.cs:34:32:34:32 | i |
+| Program.cs:34:32:34:32 | i |
+| Program.cs:34:32:34:32 | i |
+| Program.cs:37:13:37:15 | value |
+| Program.cs:45:13:45:15 | value |
+| Program.cs:49:13:49:18 | value |
+| Program.cs:55:50:55:50 | a |
+| Program.cs:55:61:55:61 | b |
+operators
+| A.cs:44:34:44:34 | + |
+| Program.cs:55:40:55:40 | - |
+constructors
+| A.cs:10:16:10:16 | A |
+| Program.cs:21:16:21:22 | Program |
+destructors
+| A.cs:16:10:16:10 | ~A |
+| Program.cs:27:10:27:16 | ~Program |
+fields
+| A.cs:9:24:9:27 | name |
+| Program.cs:19:24:19:34 | programName |
+properties
+| A.cs:21:23:21:26 | Prop |
+| Program.cs:32:23:32:33 | ProgramProp |
+indexers
+| A.cs:23:23:23:26 | Item |
+| Program.cs:34:23:34:26 | Item |
+accessors
+| A.cs:21:30:21:32 | get_Prop |
+| A.cs:21:35:21:37 | set_Prop |
+| A.cs:25:13:25:15 | get_Item |
+| A.cs:26:13:26:15 | set_Item |
+| A.cs:34:13:34:15 | add_Clicked |
+| A.cs:38:13:38:18 | remove_Clicked |
+| Program.cs:32:37:32:39 | get_ProgramProp |
+| Program.cs:32:42:32:44 | set_ProgramProp |
+| Program.cs:36:13:36:15 | get_Item |
+| Program.cs:37:13:37:15 | set_Item |
+| Program.cs:45:13:45:15 | add_ProgramClicked |
+| Program.cs:49:13:49:18 | remove_ProgramClicked |
+attributes
+| A.cs:49:10:49:19 | [MyObsolete(...)] |
+| Program.cs:60:10:60:16 | [Program(...)] |
+events
+| A.cs:32:35:32:41 | Clicked |
+| Program.cs:43:35:43:48 | ProgramClicked |
+eventAccessors
+| A.cs:34:13:34:15 | add_Clicked |
+| A.cs:38:13:38:18 | remove_Clicked |
+| Program.cs:45:13:45:15 | add_ProgramClicked |
+| Program.cs:49:13:49:18 | remove_ProgramClicked |
+usingDirectives
+| A.cs:1:1:1:13 | using ...; |
+| Program.cs:1:1:1:13 | using ...; |
+commentLines
+| A.cs:15:9:15:21 | // ... |
+| A.cs:29:9:29:10 | /* ... */ |
+| A.cs:30:1:30:27 | /* ... */ |
+| A.cs:31:1:31:11 | /* ... */ |
+| Program.cs:26:9:26:29 | // ... |
+| Program.cs:40:9:40:10 | /* ... */ |
+| Program.cs:41:1:41:27 | /* ... */ |
+| Program.cs:42:1:42:11 | /* ... */ |
+commentBlocks
+| A.cs:15:9:15:21 | // ... |
+| A.cs:29:9:31:11 | /* ... */ |
+| Program.cs:26:9:26:29 | // ... |
+| Program.cs:40:9:42:11 | /* ... */ |
+typeMentions
+| A.cs:9:17:9:22 | String |
+| A.cs:10:18:10:23 | String |
+| A.cs:18:13:18:19 | Console |
+| A.cs:21:16:21:21 | String |
+| A.cs:23:16:23:21 | Object |
+| A.cs:23:28:23:30 | Int32 |
+| A.cs:25:30:25:35 | Object |
+| A.cs:36:17:36:23 | Console |
+| A.cs:40:17:40:23 | Console |
+| A.cs:44:23:44:23 | A |
+| A.cs:44:36:44:36 | A |
+| A.cs:44:41:44:41 | A |
+| A.cs:49:10:49:19 | MyObsoleteAttribute |
+| A.cs:50:16:50:19 | Void |
+| A.cs:53:25:53:30 | String |
+| A.cs:55:13:55:18 | String |
+| A.cs:60:16:60:19 | Void |
+| A.cs:69:40:69:48 | Attribute |
+| Program.cs:7:23:7:26 | Void |
+| Program.cs:7:33:7:38 | String |
+| Program.cs:7:33:7:40 | String[] |
+| Program.cs:11:17:11:23 | Console |
+| Program.cs:14:13:14:15 | String |
+| Program.cs:15:13:15:15 | A |
+| Program.cs:15:25:15:25 | A |
+| Program.cs:16:13:16:19 | Console |
+| Program.cs:19:17:19:22 | String |
+| Program.cs:21:24:21:29 | String |
+| Program.cs:29:13:29:19 | Console |
+| Program.cs:32:16:32:21 | String |
+| Program.cs:34:16:34:21 | String |
+| Program.cs:34:28:34:30 | Int32 |
+| Program.cs:36:26:36:31 | String |
+| Program.cs:47:17:47:23 | Console |
+| Program.cs:51:17:51:23 | Console |
+| Program.cs:55:23:55:29 | Program |
+| Program.cs:55:42:55:48 | Program |
+| Program.cs:55:53:55:59 | Program |
+| Program.cs:60:10:60:16 | ProgramAttribute |
+| Program.cs:61:16:61:19 | Void |
+| Program.cs:64:37:64:45 | Attribute |
+xmlLocatables
+| web.changed.config:2:1:5:17 | configuration |
+| web.changed.config:3:3:4:16 | system.web |
+| web.unchanged.config:2:1:6:17 | configuration |
+| web.unchanged.config:3:3:5:16 | system.web |
+| web.unchanged.config:4:5:4:37 | httpCookies |
+| web.unchanged.config:4:5:4:37 | requireSSL=true |

csharp/ql/test/library-tests/overlay/overlay/test.qlref

@@ -0,0 +1 @@
+query: ../test.ql

csharp/ql/test/library-tests/overlay/overlay/web.changed.config

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+  <system.web>
+  </system.web>
+</configuration>

csharp/ql/test/library-tests/overlay/overlay/web.unchanged.config

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+  <system.web>
+    <httpCookies requireSSL="true"/>
+  </system.web>
+</configuration>

csharp/ql/test/library-tests/overlay/test.ql

@@ -0,0 +1,41 @@
+import csharp
+
+query predicate expressions(Expr e) { e.fromSource() }
+
+query predicate statements(Stmt s) { s.fromSource() }
+
+query predicate methods(Method m) { m.fromSource() }
+
+query predicate types(Type t) { t.fromSource() }
+
+query predicate parameters(Parameter p) { p.fromSource() }
+
+query predicate operators(Operator o) { o.fromSource() }
+
+query predicate constructors(Constructor c) { c.fromSource() }
+
+query predicate destructors(Destructor d) { d.fromSource() }
+
+query predicate fields(Field f) { f.fromSource() }
+
+query predicate properties(Property p) { p.fromSource() }
+
+query predicate indexers(Indexer i) { i.fromSource() }
+
+query predicate accessors(Accessor a) { a.fromSource() }
+
+query predicate attributes(Attribute a) { a.fromSource() }
+
+query predicate events(Event ev) { ev.fromSource() }
+
+query predicate eventAccessors(EventAccessor ea) { ea.fromSource() }
+
+query predicate usingDirectives(UsingDirective ud) { ud.fromSource() }
+
+query predicate commentLines(CommentLine cl) { any() }
+
+query predicate commentBlocks(CommentBlock cb) { any() }
+
+query predicate typeMentions(TypeMention tm) { any() }
+
+query predicate xmlLocatables(XmlLocatable xl) { any() }

csharp/ql/test/library-tests/overlay/testlocations.expected

@@ -0,0 +1,5 @@
+elementsWithMultipleSourceLocations
+typeMentionsWithMultipleSourceLocations
+commentLinesWithMultipleSourceLocations
+commentBlocksWithMultipleSourceLocations
+removedEntities

csharp/ql/test/library-tests/overlay/testlocations.ql

@@ -0,0 +1,29 @@
+import csharp
+
+// This is a consistency check that the overlay mechanism for cleaning up locations
+// works correctly.
+query predicate elementsWithMultipleSourceLocations(Element e, SourceLocation loc) {
+  e.fromSource() and
+  not e instanceof Namespace and
+  strictcount(SourceLocation l0 | l0 = e.getALocation()) > 1 and
+  loc = e.getALocation()
+}
+
+query predicate typeMentionsWithMultipleSourceLocations(TypeMention tm, SourceLocation loc) {
+  strictcount(SourceLocation l0 | l0 = tm.getLocation()) > 1 and
+  loc = tm.getLocation()
+}
+
+query predicate commentLinesWithMultipleSourceLocations(CommentLine cl, SourceLocation loc) {
+  strictcount(SourceLocation l0 | l0 = cl.getLocation()) > 1 and
+  loc = cl.getLocation()
+}
+
+query predicate commentBlocksWithMultipleSourceLocations(CommentBlock cb, SourceLocation loc) {
+  strictcount(SourceLocation l0 | l0 = cb.getLocation()) > 1 and
+  loc = cb.getLocation()
+}
+
+// This is a consistency check that the entities that are removed as a part of
+// the changes in the overlay are indeed removed from the database.
+query predicate removedEntities(Element e) { e.(Method).getName() = "OldMethod" }