C#: Rename GeneratedLocation to EmptyLocation and make sure that we always create one such location.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Entities/Locations/GeneratedLocation.cs renamed to 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/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);