C#: Re-use the GetTargetSymbol logic from invocations to find the right operator symbol (operators can also be declared in extensions).

Author: michaelnebel

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

@@ -228,6 +228,41 @@ type.SpecialType is SpecialType.System_IntPtr ||
             return Literal.CreateGenerated(cx, parent, childIndex, type, defaultValue, location);
         }
 
+        /// <summary>
+        /// Given an expression syntax node, attempt to resolve the target method symbol for it.
+        /// The operation takes extension methods into account.
+        /// </summary>
+        /// <param name="node">The expression syntax node.</param>
+        /// <returns>Returns the target method symbol, or null if it cannot be resolved.</returns>
+        protected IMethodSymbol? GetTargetSymbol(ExpressionSyntax node)
+        {
+            var si = Context.GetSymbolInfo(node);
+            if (si.Symbol is ISymbol symbol)
+            {
+                var method = symbol as IMethodSymbol;
+                // Case for compiler-generated extension methods.
+                return method?.TryGetExtensionMethod() ?? method;
+            }
+
+            if (si.CandidateReason == CandidateReason.OverloadResolutionFailure && node is InvocationExpressionSyntax syntax)
+            {
+                // This seems to be a bug in Roslyn
+                // For some reason, typeof(X).InvokeMember(...) fails to resolve the correct
+                // InvokeMember() method, even though the number of parameters clearly identifies the correct method
+
+                var candidates = si.CandidateSymbols
+                    .OfType<IMethodSymbol>()
+                    .Where(method => method.Parameters.Length >= syntax.ArgumentList.Arguments.Count)
+                    .Where(method => method.Parameters.Count(p => !p.HasExplicitDefaultValue) <= syntax.ArgumentList.Arguments.Count);
+
+                return Context.ExtractionContext.IsStandalone ?
+                    candidates.FirstOrDefault() :
+                    candidates.SingleOrDefault();
+            }
+
+            return si.Symbol as IMethodSymbol;
+        }
+
         /// <summary>
         /// Adapt the operator kind depending on whether it's a dynamic call or a user-operator call.
         /// </summary>
@@ -244,10 +279,10 @@ public static ExprKind UnaryOperatorKind(Context cx, ExprKind originalKind, Expr
         /// name if available.
         /// </summary>
         /// <param name="node">The expression.</param>
-        public void OperatorCall(TextWriter trapFile, ExpressionSyntax node)
+        public void AddOperatorCall(TextWriter trapFile, ExpressionSyntax node)
         {
-            var @operator = Context.GetSymbolInfo(node);
-            if (@operator.Symbol is IMethodSymbol method)
+            var @operator = GetTargetSymbol(node);
+            if (@operator is IMethodSymbol method)
             {
                 var callType = GetCallType(Context, node);
                 if (callType == CallType.Dynamic)

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

@@ -24,10 +24,9 @@ protected override void PopulateExpression(TextWriter trapFile)
         {
             Create(Context, Syntax.Left, this, 0);
             Create(Context, Syntax.Right, this, 1);
-
             if (Kind != ExprKind.SIMPLE_ASSIGN && Kind != ExprKind.ASSIGN_COALESCE)
             {
-                OperatorCall(trapFile, Syntax);
+                AddOperatorCall(trapFile, Syntax);
             }
         }
 

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

@@ -40,7 +40,7 @@ private void CreateDeferred(Context cx, ExpressionSyntax node, int child)
 
         protected override void PopulateExpression(TextWriter trapFile)
         {
-            OperatorCall(trapFile, Syntax);
+            AddOperatorCall(trapFile, Syntax);
             CreateDeferred(Context, Syntax.Left, 0);
             CreateDeferred(Context, Syntax.Right, 1);
         }

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

@@ -25,7 +25,7 @@ protected override void PopulateExpression(TextWriter trapFile)
             else
             {
                 // Type conversion
-                OperatorCall(trapFile, Syntax);
+                AddOperatorCall(trapFile, Syntax);
                 TypeMention.Create(Context, Syntax.Type, this, Type);
             }
         }

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

@@ -44,7 +44,7 @@ protected override void PopulateExpression(TextWriter trapFile)
 
             var child = -1;
             string? memberName = null;
-            var target = TargetSymbol;
+            var target = GetTargetSymbol(Syntax);
             switch (Syntax.Expression)
             {
                 case MemberAccessExpressionSyntax memberAccess when IsValidMemberAccessKind():
@@ -129,39 +129,6 @@ private static bool IsOperatorLikeCall(ExpressionNodeInfo info)
                 method.TryGetExtensionMethod()?.MethodKind == MethodKind.UserDefinedOperator;
         }
 
-        public IMethodSymbol? TargetSymbol
-        {
-            get
-            {
-                var si = SymbolInfo;
-
-                if (si.Symbol is ISymbol symbol)
-                {
-                    var method = symbol as IMethodSymbol;
-                    // Case for compiler-generated extension methods.
-                    return method?.TryGetExtensionMethod() ?? method;
-                }
-
-                if (si.CandidateReason == CandidateReason.OverloadResolutionFailure)
-                {
-                    // This seems to be a bug in Roslyn
-                    // For some reason, typeof(X).InvokeMember(...) fails to resolve the correct
-                    // InvokeMember() method, even though the number of parameters clearly identifies the correct method
-
-                    var candidates = si.CandidateSymbols
-                        .OfType<IMethodSymbol>()
-                        .Where(method => method.Parameters.Length >= Syntax.ArgumentList.Arguments.Count)
-                        .Where(method => method.Parameters.Count(p => !p.HasExplicitDefaultValue) <= Syntax.ArgumentList.Arguments.Count);
-
-                    return Context.ExtractionContext.IsStandalone ?
-                        candidates.FirstOrDefault() :
-                        candidates.SingleOrDefault();
-                }
-
-                return si.Symbol as IMethodSymbol;
-            }
-        }
-
         private static bool IsDelegateLikeCall(ExpressionNodeInfo info)
         {
             return IsDelegateLikeCall(info, symbol => IsFunctionPointer(symbol) || IsDelegateInvoke(symbol));

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

@@ -25,7 +25,7 @@ protected override void PopulateExpression(TextWriter trapFile)
             if ((operatorKind == ExprKind.POST_INCR || operatorKind == ExprKind.POST_DECR) &&
                 Kind == ExprKind.OPERATOR_INVOCATION)
             {
-                OperatorCall(trapFile, Syntax);
+                AddOperatorCall(trapFile, Syntax);
                 trapFile.mutator_invocation_mode(this, 2);
             }
         }

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

@@ -24,7 +24,7 @@ public static Unary Create(ExpressionNodeInfo info)
         protected override void PopulateExpression(TextWriter trapFile)
         {
             Create(Context, Syntax.Operand, this, 0);
-            OperatorCall(trapFile, Syntax);
+            AddOperatorCall(trapFile, Syntax);
 
             if ((operatorKind == ExprKind.PRE_INCR || operatorKind == ExprKind.PRE_DECR) &&
                 Kind == ExprKind.OPERATOR_INVOCATION)