C#: Reduce location tuples.

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

@@ -63,8 +63,10 @@ public override void Populate(TextWriter trapFile)
 
             trapFile.accessors(this, kind, Symbol.Name, parent, unboundAccessor);
 
-            foreach (var l in Locations)
-                trapFile.accessor_location(this, l);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.accessor_location, this, Locations);
+            }
 
             Overrides(trapFile);
 

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

@@ -59,11 +59,11 @@ public override void Populate(TextWriter trapFile)
         {
             var type = Type.Create(Context, Symbol.AttributeClass);
             trapFile.attributes(this, kind, type.TypeRef, entity);
-            trapFile.attribute_location(this, Location);
+            WriteLocationToTrap(trapFile.attribute_location, this, Location);
 
             if (attributeSyntax is not null)
             {
-                trapFile.attribute_location(this, Assembly.CreateOutputAssembly(Context));
+                WriteLocationToTrap(trapFile.attribute_location, this, Assembly.CreateOutputAssembly(Context));
 
                 TypeMention.Create(Context, attributeSyntax.Name, this, type);
             }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Base/CachedEntity.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using Microsoft.CodeAnalysis;
@@ -52,6 +54,22 @@ public string DebugContents
             }
         }
 
+        protected static void WriteLocationToTrap<T1>(Action<T1, Location> writeAction, T1 entity, Location l)
+        {
+            if (l is not EmptyLocation)
+            {
+                writeAction(entity, l);
+            }
+        }
+
+        protected static void WriteLocationsToTrap<T1>(Action<T1, Location> writeAction, T1 entity, IEnumerable<Location> locations)
+        {
+            foreach (var loc in locations)
+            {
+                WriteLocationToTrap(writeAction, entity, loc);
+            }
+        }
+
         public override bool NeedsPopulation { get; }
 
         public override int GetHashCode() => Symbol is null ? 0 : Symbol.GetHashCode();

csharp/extractor/Semmle.Extraction.CSharp/Entities/Base/CachedSymbol.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;

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

@@ -11,7 +11,7 @@ private CommentBlock(Context cx, Comments.CommentBlock init)
         public override void Populate(TextWriter trapFile)
         {
             trapFile.commentblock(this);
-            trapFile.commentblock_location(this, Context.CreateLocation(Symbol.Location));
+            WriteLocationToTrap(trapFile.commentblock_location, this, Context.CreateLocation(Symbol.Location));
             Symbol.CommentLines.ForEach((l, child) => trapFile.commentblock_child(this, l, child));
         }
 

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

@@ -23,7 +23,7 @@ public override void Populate(TextWriter trapFile)
         {
             location = Context.CreateLocation(Location);
             trapFile.commentline(this, Type == CommentLineType.MultilineContinuation ? CommentLineType.Multiline : Type, Text, RawText);
-            trapFile.commentline_location(this, location);
+            WriteLocationToTrap(trapFile.commentline_location, this, location);
         }
 
         public override Microsoft.CodeAnalysis.Location? ReportingLocation => location?.Symbol;

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

@@ -29,7 +29,7 @@ public override void Populate(TextWriter trapFile)
             ContainingType!.PopulateGenerics();
 
             trapFile.constructors(this, Symbol.ContainingType.Name, ContainingType, (Constructor)OriginalDefinition);
-            trapFile.constructor_location(this, Location);
+            WriteLocationToTrap(trapFile.constructor_location, this, Location);
 
             if (MakeSynthetic)
             {

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

@@ -15,7 +15,7 @@ public override void Populate(TextWriter trapFile)
             ContainingType!.PopulateGenerics();
 
             trapFile.destructors(this, $"~{Symbol.ContainingType.Name}", ContainingType, OriginalDefinition(Context, this, Symbol));
-            trapFile.destructor_location(this, Location);
+            WriteLocationToTrap(trapFile.destructor_location, this, Location);
         }
 
         private static new Destructor OriginalDefinition(Context cx, Destructor original, IMethodSymbol symbol)

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

@@ -51,8 +51,10 @@ public override void Populate(TextWriter trapFile)
                     TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
-            foreach (var l in Locations)
-                trapFile.event_location(this, l);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.event_location, this, Locations);
+            }
 
             foreach (var syntaxType in declSyntaxReferences
                 .OfType<VariableDeclaratorSyntax>()

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

@@ -48,8 +48,10 @@ public override void Populate(TextWriter trapFile)
 
             trapFile.event_accessors(this, kind, Symbol.Name, parent, unboundAccessor);
 
-            foreach (var l in Locations)
-                trapFile.event_accessor_location(this, l);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.event_accessor_location, this, Locations);
+            }
 
             Overrides(trapFile);
 

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

@@ -40,6 +40,7 @@ protected sealed override void Populate(TextWriter trapFile)
                 trapFile.expr_parent_top_level(this, info.Child, info.Parent);
             else
                 trapFile.expr_parent(this, info.Child, info.Parent);
+
             trapFile.expr_location(this, Location);
 
             if (Type.HasValue && !Type.Value.HasObliviousNullability())

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

@@ -49,8 +49,7 @@ public override void Populate(TextWriter trapFile)
                 }
             }
 
-            foreach (var l in Locations)
-                trapFile.field_location(this, l);
+            WriteLocationsToTrap(trapFile.field_location, this, Locations);
 
             if (!IsSourceDeclaration || !Symbol.FromSource())
                 return;

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

@@ -19,8 +19,10 @@ public override void Populate(TextWriter trapFile)
 
             var type = Type.Create(Context, Symbol.Type);
             trapFile.indexers(this, Symbol.GetName(useMetadataName: true), ContainingType!, type.TypeRef, OriginalDefinition);
-            foreach (var l in Locations)
-                trapFile.indexer_location(this, l);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.indexer_location, this, Locations);
+            }
 
             var getter = BodyDeclaringSymbol.GetMethod;
             var setter = BodyDeclaringSymbol.SetMethod;

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

@@ -41,7 +41,7 @@ public void PopulateManual(Expression parent, bool isVar)
                 trapFile.localvars(this, Kinds.VariableKind.None, Symbol.Name, @var, Type.Create(Context, parent.Type).TypeRef, parent);
             }
 
-            trapFile.localvar_location(this, Location);
+            WriteLocationToTrap(trapFile.localvar_location, this, Location);
 
             DefineConstantValue(trapFile);
         }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Locations/GeneratedLocation.cs → csharp/extractor/Semmle.Extraction.CSharp/Entities/Locations/EmptyLocation.cs

@@ -2,11 +2,11 @@
 
 namespace Semmle.Extraction.CSharp.Entities
 {
-    public class GeneratedLocation : SourceLocation
+    public class EmptyLocation : SourceLocation
     {
         private readonly File generatedFile;
 
-        private GeneratedLocation(Context cx)
+        private EmptyLocation(Context cx)
             : base(cx, null)
         {
             generatedFile = GeneratedFile.Create(cx);
@@ -26,15 +26,16 @@ public override void WriteId(EscapingTextWriter trapFile)
 
         public override int GetHashCode() => 98732567;
 
-        public override bool Equals(object? obj) => obj is not null && obj.GetType() == typeof(GeneratedLocation);
+        public override bool Equals(object? obj) => obj is not null && obj.GetType() == typeof(EmptyLocation);
 
-        public static GeneratedLocation Create(Context cx) => GeneratedLocationFactory.Instance.CreateEntity(cx, typeof(GeneratedLocation), null);
+        public static EmptyLocation Create(Context cx)
+            => EmptyLocationFactory.Instance.CreateEntity(cx, typeof(EmptyLocation), null);
 
-        private class GeneratedLocationFactory : CachedEntityFactory<string?, GeneratedLocation>
+        private class EmptyLocationFactory : CachedEntityFactory<string?, EmptyLocation>
         {
-            public static GeneratedLocationFactory Instance { get; } = new GeneratedLocationFactory();
+            public static EmptyLocationFactory Instance { get; } = new EmptyLocationFactory();
 
-            public override GeneratedLocation Create(Context cx, string? init) => new GeneratedLocation(cx);
+            public override EmptyLocation Create(Context cx, string? init) => new EmptyLocation(cx);
         }
     }
 }

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

@@ -35,7 +35,7 @@ public override void Populate(TextWriter trapFile)
 
             var ns = Namespace.Create(Context, @namespace);
             trapFile.namespace_declarations(this, ns);
-            trapFile.namespace_declaration_location(this, Context.CreateLocation(node.Name.GetLocation()));
+            WriteLocationToTrap(trapFile.namespace_declaration_location, this, Context.CreateLocation(node.Name.GetLocation()));
 
             var visitor = new Populators.TypeOrNamespaceVisitor(Context, trapFile, this);
 

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

@@ -43,8 +43,10 @@ public override void Populate(TextWriter trapFile)
                 }
             }
 
-            foreach (var l in Locations)
-                trapFile.method_location(this, l);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.method_location, this, Locations);
+            }
 
             PopulateGenerics(trapFile);
             Overrides(trapFile);

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

@@ -116,14 +116,16 @@ public override void Populate(TextWriter trapFile)
             trapFile.@params(this, Name, type.TypeRef, Ordinal, ParamKind, Parent!, Original);
 
             foreach (var l in Symbol.Locations)
-                trapFile.param_location(this, Context.CreateLocation(l));
+            {
+                WriteLocationToTrap(trapFile.param_location, this, Context.CreateLocation(l));
+            }
 
             if (!Symbol.Locations.Any() &&
                 Symbol.ContainingSymbol is IMethodSymbol ms &&
                 ms.Name == WellKnownMemberNames.TopLevelStatementsEntryPointMethodName &&
                 ms.ContainingType.Name == WellKnownMemberNames.TopLevelStatementsEntryPointTypeName)
             {
-                trapFile.param_location(this, Context.CreateLocation());
+                WriteLocationToTrap(trapFile.param_location, this, Context.CreateLocation());
             }
 
             if (Symbol.HasExplicitDefaultValue && Context.Defines(Symbol))
@@ -247,7 +249,6 @@ public override void Populate(TextWriter trapFile)
             var typeKey = VarargsType.Create(Context);
             // !! Maybe originaldefinition is wrong
             trapFile.@params(this, "", typeKey, Ordinal, Kind.None, Parent!, this);
-            trapFile.param_location(this, GeneratedLocation.Create(Context));
         }
 
         protected override int Ordinal => ((Method)Parent!).OriginalDefinition.Symbol.Parameters.Length;

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

@@ -13,7 +13,7 @@ public sealed override void Populate(TextWriter trapFile)
             PopulatePreprocessor(trapFile);
 
             trapFile.preprocessor_directive_active(this, Symbol.IsActive);
-            trapFile.preprocessor_directive_location(this, Context.CreateLocation(ReportingLocation));
+            WriteLocationToTrap(trapFile.preprocessor_directive_location, this, Context.CreateLocation(ReportingLocation));
 
             var compilation = Compilation.Create(Context);
             trapFile.preprocessor_directive_compilation(this, compilation);

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

@@ -69,8 +69,10 @@ public override void Populate(TextWriter trapFile)
                     TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
-            foreach (var l in Locations)
-                trapFile.property_location(this, l);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.property_location, this, Locations);
+            }
 
             if (IsSourceDeclaration && Symbol.FromSource())
             {

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

@@ -16,7 +16,7 @@ private DynamicType(Context cx, IDynamicTypeSymbol init)
         public override void Populate(TextWriter trapFile)
         {
             trapFile.types(this, Kinds.TypeKind.DYNAMIC, "dynamic");
-            trapFile.type_location(this, Location);
+            WriteLocationToTrap(trapFile.type_location, this, Location);
 
             trapFile.has_modifiers(this, Modifier.Create(Context, "public"));
             trapFile.parent_namespace(this, Namespace.Create(Context, Context.Compilation.GlobalNamespace));

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

@@ -83,8 +83,7 @@ public override void Populate(TextWriter trapFile)
             // Class location
             if (!Symbol.IsGenericType || Symbol.IsReallyUnbound())
             {
-                foreach (var l in Locations)
-                    trapFile.type_location(this, l);
+                WriteLocationsToTrap(trapFile.type_location, this, Locations);
             }
 
             if (Symbol.IsAnonymousType)

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

@@ -55,7 +55,7 @@ public override void Populate(TextWriter trapFile)
             // about what locations are available for a tuple type.
             // Sometimes it's the source code, and sometimes it's empty.
             foreach (var l in Symbol.Locations)
-                trapFile.type_location(this, Context.CreateLocation(l));
+                WriteLocationToTrap(trapFile.type_location, this, Context.CreateLocation(l));
         }
 
         private readonly Lazy<Field?[]> tupleElementsLazy;

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

@@ -28,7 +28,7 @@ public override void Populate(TextWriter trapFile)
 
             foreach (var l in Symbol.Locations)
             {
-                trapFile.type_location(this, Context.CreateLocation(l));
+                WriteLocationToTrap(trapFile.type_location, this, Context.CreateLocation(l));
             }
 
             if (IsSourceDeclaration)

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

@@ -26,8 +26,7 @@ public override void Populate(TextWriter trapFile)
                 returnType.TypeRef,
                 (UserOperator)OriginalDefinition);
 
-            foreach (var l in Locations)
-                trapFile.operator_location(this, l);
+            WriteLocationsToTrap(trapFile.operator_location, this, Locations);
 
             if (IsSourceDeclaration)
             {

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

@@ -238,6 +238,9 @@ private void DoAnalyseCompilation()
 
                 compilationEntity = Entities.Compilation.Create(cx);
 
+                // Ensure that the empty location is always created.
+                Entities.EmptyLocation.Create(cx);
+
                 ExtractionContext.CompilationInfos.ForEach(ci => trapWriter.Writer.compilation_info(compilationEntity, ci.key, ci.value));
 
                 ReportProgressTaskDone(currentTaskId, assemblyPath, trapWriter.TrapFile, stopwatch.Elapsed, AnalysisAction.Extracted);

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

@@ -550,6 +550,10 @@ public bool Defines(ISymbol symbol) =>
             !SymbolEqualityComparer.Default.Equals(symbol, symbol.OriginalDefinition) ||
             scope.InScope(symbol);
 
+        public bool ExtractLocation(ISymbol symbol) =>
+            SymbolEqualityComparer.Default.Equals(symbol, symbol.OriginalDefinition) &&
+            scope.InScope(symbol);
+
         /// <summary>
         /// Runs the given action <paramref name="a"/>, guarding for trap duplication
         /// based on key <paramref name="key"/>.
@@ -582,14 +586,14 @@ public void WithDuplicationGuard(Key key, Action a)
         public Entities.Location CreateLocation()
         {
             return SourceTree is null
-                ? Entities.GeneratedLocation.Create(this)
+                ? Entities.EmptyLocation.Create(this)
                 : CreateLocation(Microsoft.CodeAnalysis.Location.Create(SourceTree, Microsoft.CodeAnalysis.Text.TextSpan.FromBounds(0, 0)));
         }
 
         public Entities.Location CreateLocation(Microsoft.CodeAnalysis.Location? location)
         {
             return (location is null || location.Kind == LocationKind.None)
-                ? Entities.GeneratedLocation.Create(this)
+                ? Entities.EmptyLocation.Create(this)
                 : location.IsInSource
                     ? Entities.NonGeneratedSourceLocation.Create(this, location)
                     : Entities.Assembly.Create(this, location);

csharp/ql/lib/change-notes/2025-10-02-entity-locations.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* The extraction of the location for bound generic entities (methods, accessors, indexers, properties, and events) has been optimized. Previously, location information was extracted multiple times for each bound generic. Now, only the location of the unbound generic declaration is extracted during the extraction phase, and the QL library explicitly reuses this location for all bound instances of the same generic.

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

@@ -265,7 +265,7 @@ class Method extends Callable, Virtualizable, Attributable, @method {
     result = Virtualizable.super.getAnUltimateImplementor()
   }
 
-  override Location getALocation() { method_location(this, result) }
+  override Location getALocation() { method_location(this.getUnboundDeclaration(), result) }
 
   /** Holds if this method is an extension method. */
   predicate isExtensionMethod() { this.getParameter(0).hasExtensionMethodModifier() }

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

@@ -68,7 +68,7 @@ class Event extends DeclarationWithAccessors, @event {
     result = DeclarationWithAccessors.super.getAnUltimateImplementor()
   }
 
-  override Location getALocation() { event_location(this, result) }
+  override Location getALocation() { event_location(this.getUnboundDeclaration(), result) }
 
   override string getAPrimaryQlClass() { result = "Event" }
 }
@@ -99,7 +99,7 @@ class EventAccessor extends Accessor, @event_accessor {
 
   override Event getDeclaration() { event_accessors(this, _, _, result, _) }
 
-  override Location getALocation() { event_accessor_location(this, result) }
+  override Location getALocation() { event_accessor_location(this.getUnboundDeclaration(), result) }
 }
 
 /**