C#: Avoid extracting duplicate type locations.

Author: michaelnebel

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

@@ -111,15 +111,18 @@ public override IEnumerable<Location> Locations
             }
         }
 
-        private static IEnumerable<Microsoft.CodeAnalysis.Location> GetLocations(INamedTypeSymbol type)
+        private IEnumerable<Microsoft.CodeAnalysis.Location> GetLocations(INamedTypeSymbol type)
         {
-            return type.Locations
-                .Where(l => l.IsInMetadata)
-                .Concat(type.DeclaringSyntaxReferences
+            var metadataLocations = type.Locations
+                .Where(l => l.IsInMetadata);
+            var sourceLocations = type.DeclaringSyntaxReferences
                     .Select(loc => loc.GetSyntax())
                     .OfType<CSharpSyntaxNode>()
                     .Select(l => l.FixedLocation())
-                );
+                    .Where(Context.IsLocationInContext);
+
+            return metadataLocations
+                .Concat(sourceLocations);
         }
 
         public override Microsoft.CodeAnalysis.Location? ReportingLocation => GetLocations(Symbol).BestOrDefault();

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

@@ -26,9 +26,12 @@ public override void Populate(TextWriter trapFile)
             var parentNs = Namespace.Create(Context, Symbol.TypeParameterKind == TypeParameterKind.Method ? Context.Compilation.GlobalNamespace : Symbol.ContainingNamespace);
             trapFile.parent_namespace(this, parentNs);
 
-            foreach (var l in Symbol.Locations)
+            if (Context.ExtractLocation(Symbol))
             {
-                WriteLocationToTrap(trapFile.type_location, this, Context.CreateLocation(l));
+                foreach (var l in Symbol.Locations)
+                {
+                    WriteLocationToTrap(trapFile.type_location, this, Context.CreateLocation(l));
+                }
             }
 
             if (IsSourceDeclaration)

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

@@ -554,6 +554,9 @@ public bool ExtractLocation(ISymbol symbol) =>
             SymbolEqualityComparer.Default.Equals(symbol, symbol.OriginalDefinition) &&
             scope.InScope(symbol);
 
+        public bool IsLocationInContext(Location location) =>
+            location.SourceTree == SourceTree;
+
         /// <summary>
         /// Runs the given action <paramref name="a"/>, guarding for trap duplication
         /// based on key <paramref name="key"/>.