C#: Fix extraction of qualified delegate calls

Author: hvitved

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Invocation.cs

@@ -20,6 +20,10 @@ private Invocation(ExpressionNodeInfo info)
 
         public static Expression Create(ExpressionNodeInfo info) => new Invocation(info).TryPopulate();
 
+        private bool IsEventDelegateCall() => Kind == ExprKind.DELEGATE_INVOCATION && Context.GetModel(Syntax.Expression).GetSymbolInfo(Syntax.Expression).Symbol?.Kind == SymbolKind.Event;
+
+        private bool IsExplicitDelegateInvokeCall() => Kind == ExprKind.DELEGATE_INVOCATION && Context.GetModel(Syntax.Expression).GetSymbolInfo(Syntax.Expression).Symbol is IMethodSymbol m && m.MethodKind == MethodKind.DelegateInvoke;
+
         protected override void PopulateExpression(TextWriter trapFile)
         {
             if (IsNameof(Syntax))
@@ -33,7 +37,7 @@ protected override void PopulateExpression(TextWriter trapFile)
             var target = TargetSymbol;
             switch (Syntax.Expression)
             {
-                case MemberAccessExpressionSyntax memberAccess:
+                case MemberAccessExpressionSyntax memberAccess when Kind == ExprKind.METHOD_INVOCATION || IsEventDelegateCall() || IsExplicitDelegateInvokeCall():
                     memberName = memberAccess.Name.Identifier.Text;
                     if (Syntax.Expression.Kind() == SyntaxKind.SimpleMemberAccessExpression)
                         // Qualified method call; `x.M()`
@@ -48,7 +52,7 @@ protected override void PopulateExpression(TextWriter trapFile)
                     Create(Context, FindConditionalQualifier(memberBinding), this, child++);
                     MakeConditional(trapFile);
                     break;
-                case SimpleNameSyntax simpleName when (Kind == ExprKind.METHOD_INVOCATION):
+                case SimpleNameSyntax simpleName when Kind == ExprKind.METHOD_INVOCATION:
                     // Unqualified method call; `M()`
                     memberName = simpleName.Identifier.Text;
                     if (target is not null && !target.IsStatic)

csharp/ql/test/library-tests/delegates/Delegates4.expected

@@ -2,7 +2,7 @@
 | delegates.cs:74:13:74:23 | delegate call | delegates.cs:74:13:74:15 | access to local variable cd7 |
 | delegates.cs:79:22:79:26 | delegate call | delegates.cs:79:22:79:23 | access to local variable pi |
 | delegates.cs:79:30:79:35 | delegate call | delegates.cs:79:30:79:31 | access to local variable ps |
-| delegates.cs:93:13:93:25 | delegate call | delegates.cs:93:13:93:16 | this access |
-| delegates.cs:94:13:94:28 | delegate call | delegates.cs:94:13:94:16 | this access |
+| delegates.cs:93:13:93:25 | delegate call | delegates.cs:93:13:93:22 | access to field Field |
+| delegates.cs:94:13:94:28 | delegate call | delegates.cs:94:13:94:25 | access to property Property |
 | delegates.cs:95:13:95:20 | delegate call | delegates.cs:95:13:95:17 | access to field Field |
 | delegates.cs:96:13:96:23 | delegate call | delegates.cs:96:13:96:20 | access to property Property |

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

@@ -265,11 +265,13 @@ delegates.cs:
 #   92|       4: [BlockStmt] {...}
 #   93|         0: [ExprStmt] ...;
 #   93|           0: [DelegateCall] delegate call
-#   93|             -1: [ThisAccess] this access
+#   93|             -1: [FieldAccess] access to field Field
+#   93|               -1: [ThisAccess] this access
 #   93|             0: [IntLiteral] 0
 #   94|         1: [ExprStmt] ...;
 #   94|           0: [DelegateCall] delegate call
-#   94|             -1: [ThisAccess] this access
+#   94|             -1: [PropertyCall] access to property Property
+#   94|               -1: [ThisAccess] this access
 #   94|             0: [IntLiteral] 0
 #   95|         2: [ExprStmt] ...;
 #   95|           0: [DelegateCall] delegate call