Merge pull request #5980 from tamasvajk/fix/extension-method-as-target

C#: Extract correct method symbol as target of extension method calls

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

@@ -20,26 +20,6 @@ namespace Semmle.Extraction.CSharp.Entities
             IEnumerable<IParameterSymbol> parameters = Symbol.Parameters;
             IEnumerable<IParameterSymbol> originalParameters = originalMethod.Symbol.Parameters;
 
-            if (IsReducedExtension)
-            {
-                if (this == originalMethod)
-                {
-                    // Non-generic reduced extensions must be extracted exactly like the
-                    // non-reduced counterparts
-                    parameters = Symbol.ReducedFrom!.Parameters;
-                }
-                else
-                {
-                    // Constructed reduced extensions are special because their non-reduced
-                    // counterparts are not constructed. Therefore, we need to manually add
-                    // the `this` parameter based on the type of the receiver
-                    var originalThisParamSymbol = originalMethod.Symbol.Parameters.First();
-                    var originalThisParam = Parameter.Create(Context, originalThisParamSymbol, originalMethod);
-                    ConstructedExtensionParameter.Create(Context, this, originalThisParam);
-                    originalParameters = originalParameters.Skip(1);
-                }
-            }
-
             foreach (var p in parameters.Zip(originalParameters, (paramSymbol, originalParam) => new { paramSymbol, originalParam }))
             {
                 var original = SymbolEqualityComparer.Default.Equals(p.paramSymbol, p.originalParam)
@@ -208,9 +188,7 @@ namespace Semmle.Extraction.CSharp.Entities
             trapFile.Write('(');
             var index = 0;
 
-            var @params = method.MethodKind == MethodKind.ReducedExtension
-                ? method.ReducedFrom!.Parameters
-                : method.Parameters;
+            var @params = method.Parameters;
 
             foreach (var param in @params)
             {
@@ -272,6 +250,11 @@ namespace Semmle.Extraction.CSharp.Entities
                 case MethodKind.Constructor:
                     return Constructor.Create(cx, methodDecl);
                 case MethodKind.ReducedExtension:
+                    if (SymbolEqualityComparer.Default.Equals(methodDecl, methodDecl.ConstructedFrom))
+                    {
+                        return OrdinaryMethod.Create(cx, methodDecl.ReducedFrom!);
+                    }
+                    return OrdinaryMethod.Create(cx, methodDecl.ReducedFrom!.Construct(methodDecl.TypeArguments, methodDecl.TypeArgumentNullableAnnotations));
                 case MethodKind.Ordinary:
                 case MethodKind.DelegateInvoke:
                     return OrdinaryMethod.Create(cx, methodDecl);
@@ -297,10 +280,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        public Method OriginalDefinition =>
-            IsReducedExtension
-                ? Create(Context, Symbol.ReducedFrom!)
-                : Create(Context, Symbol.OriginalDefinition);
+        public Method OriginalDefinition => Create(Context, Symbol.OriginalDefinition);
 
         public override Location? FullLocation => ReportingLocation;
 
@@ -318,9 +298,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public bool IsBoundGeneric => IsGeneric && !IsUnboundGeneric;
 
-        private bool IsReducedExtension => Symbol.MethodKind == MethodKind.ReducedExtension;
-
-        protected IMethodSymbol ConstructedFromSymbol => Symbol.ConstructedFrom.ReducedFrom ?? Symbol.ConstructedFrom;
+        protected IMethodSymbol ConstructedFromSymbol => Symbol.ConstructedFrom;
 
         bool IExpressionParentEntity.IsTopLevelParent => true;
 

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

@@ -15,14 +15,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         protected override IMethodSymbol BodyDeclaringSymbol => Symbol.PartialImplementationPart ?? Symbol;
 
-        public IMethodSymbol SourceDeclaration
-        {
-            get
-            {
-                var reducedFrom = Symbol.ReducedFrom ?? Symbol;
-                return reducedFrom.OriginalDefinition;
-            }
-        }
+        public IMethodSymbol SourceDeclaration => Symbol.OriginalDefinition;
 
         public override Microsoft.CodeAnalysis.Location ReportingLocation => Symbol.GetSymbolLocation();
 
@@ -53,7 +46,15 @@ namespace Semmle.Extraction.CSharp.Entities
             ExtractCompilerGenerated(trapFile);
         }
 
-        public static new OrdinaryMethod Create(Context cx, IMethodSymbol method) => OrdinaryMethodFactory.Instance.CreateEntityFromSymbol(cx, method);
+        public static new OrdinaryMethod Create(Context cx, IMethodSymbol method)
+        {
+            if (method.MethodKind == MethodKind.ReducedExtension)
+            {
+                cx.Extractor.Logger.Log(Util.Logging.Severity.Warning, "Reduced extension method symbols should not be directly extracted.");
+            }
+
+            return OrdinaryMethodFactory.Instance.CreateEntityFromSymbol(cx, method);
+        }
 
         private class OrdinaryMethodFactory : CachedEntityFactory<IMethodSymbol, OrdinaryMethod>
         {

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

@@ -27,20 +27,7 @@ namespace Semmle.Extraction.CSharp.Entities
             None, Ref, Out, Params, This, In
         }
 
-        protected virtual int Ordinal
-        {
-            get
-            {
-                // For some reason, methods of kind ReducedExtension
-                // omit the "this" parameter, so the parameters are
-                // actually numbered from 1.
-                // This is to be consistent from the original (unreduced) extension method.
-                var isReducedExtension =
-                    Symbol.ContainingSymbol is IMethodSymbol method &&
-                    method.MethodKind == MethodKind.ReducedExtension;
-                return Symbol.Ordinal + (isReducedExtension ? 1 : 0);
-            }
-        }
+        protected virtual int Ordinal => Symbol.Ordinal;
 
         private Kind ParamKind
         {
@@ -270,33 +257,4 @@ namespace Semmle.Extraction.CSharp.Entities
             public override VarargsParam Create(Context cx, Method init) => new VarargsParam(cx, init);
         }
     }
-
-    internal class ConstructedExtensionParameter : Parameter
-    {
-        private readonly ITypeSymbol constructedType;
-
-        private ConstructedExtensionParameter(Context cx, Method method, Parameter original)
-            : base(cx, original.Symbol, method, original)
-        {
-            constructedType = method.Symbol.ReceiverType!;
-        }
-
-        public override void Populate(TextWriter trapFile)
-        {
-            var typeKey = Type.Create(Context, constructedType);
-            trapFile.@params(this, Original.Symbol.Name, typeKey.TypeRef, 0, Kind.This, Parent!, Original);
-            trapFile.param_location(this, Original.Location);
-        }
-
-        public static ConstructedExtensionParameter Create(Context cx, Method method, Parameter parameter) =>
-            ExtensionParamFactory.Instance.CreateEntity(cx, (new SymbolEqualityWrapper(parameter.Symbol), new SymbolEqualityWrapper(method.Symbol.ReceiverType!)), (method, parameter));
-
-        private class ExtensionParamFactory : CachedEntityFactory<(Method, Parameter), ConstructedExtensionParameter>
-        {
-            public static ExtensionParamFactory Instance { get; } = new ExtensionParamFactory();
-
-            public override ConstructedExtensionParameter Create(Context cx, (Method, Parameter) init) =>
-                new ConstructedExtensionParameter(cx, init.Item1, init.Item2);
-        }
-    }
 }