C#: Re-factor TargetSymbol into an extension method.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/CodeAnalysisExtensions/SymbolExtensions.cs

@@ -4,6 +4,7 @@
 using System.IO;
 using System.Linq;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Semmle.Util;
 using Semmle.Extraction.CSharp.Entities;
 
@@ -856,5 +857,34 @@ public static Parameter.Kind GetParameterKind(this IParameterSymbol parameter)
                     return Parameter.Kind.None;
             }
         }
+
+        public static IMethodSymbol? GetTargetSymbol(this ExpressionNodeInfo info, Context cx)
+        {
+            var si = info.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 && info.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 cx.ExtractionContext.IsStandalone ?
+                    candidates.FirstOrDefault() :
+                    candidates.SingleOrDefault();
+            }
+
+            return si.Symbol as IMethodSymbol;
+        }
     }
 }

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 = info.GetTargetSymbol(Context);
             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));