C#: Support for partial event declarations.

Author: michaelnebel

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

@@ -11,6 +11,10 @@ internal class Event : CachedSymbol<IEventSymbol>
         private Event(Context cx, IEventSymbol init)
             : base(cx, init) { }
 
+        protected override IEventSymbol BodyDeclaringSymbol => Symbol.PartialImplementationPart ?? Symbol;
+
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => BodyDeclaringSymbol.Locations.BestOrDefault();
+
         public override void WriteId(EscapingTextWriter trapFile)
         {
             trapFile.WriteSubId(ContainingType!);
@@ -27,13 +31,13 @@ public override void Populate(TextWriter trapFile)
             var type = Type.Create(Context, Symbol.Type);
             trapFile.events(this, Symbol.GetName(), ContainingType!, type.TypeRef, Create(Context, Symbol.OriginalDefinition));
 
-            var adder = Symbol.AddMethod;
-            var remover = Symbol.RemoveMethod;
+            var adder = BodyDeclaringSymbol.AddMethod;
+            var remover = BodyDeclaringSymbol.RemoveMethod;
 
-            if (!(adder is null))
+            if (adder is not null)
                 Method.Create(Context, adder);
 
-            if (!(remover is null))
+            if (remover is not null)
                 Method.Create(Context, remover);
 
             PopulateModifiers(trapFile);

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

@@ -13,6 +13,10 @@ private EventAccessor(Context cx, IMethodSymbol init, IEventSymbol @event)
             this.@event = @event;
         }
 
+        public override bool NeedsPopulation =>
+            base.NeedsPopulation &&
+            !Symbol.IsPartialDefinition; // Accessors always have an implementing declaration as well.
+
         /// <summary>
         /// Gets the event symbol associated with accessor `symbol`, or `null`
         /// if there is no associated symbol.