Merge pull request #4413 from hvitved/csharp/indexer-explicit-interface

hvitved · web-flow · commit a9bb7b526ccf · 2020-10-07T18:49:30.000+02:00
C#: Fix extraction of library indexers with explicit interface implementations
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Accessor.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Accessor.cs
@@ -10,25 +10,28 @@ protected Accessor(Context cx, IMethodSymbol init)
             : base(cx, init) { }
 
         /// <summary>
-        /// Gets the property symbol associated with this accessor.
+        /// Gets the property symbol associated accessor `symbol`, or `null`
+        /// if there is no associated symbol.
         /// </summary>
-        IPropertySymbol PropertySymbol
+        public static IPropertySymbol GetPropertySymbol(IMethodSymbol symbol)
         {
-            get
-            {
-                // Usually, the property/indexer can be fetched from the associated symbol
-                var prop = symbol.AssociatedSymbol as IPropertySymbol;
-                if (prop != null)
-                    return prop;
+            // Usually, the property/indexer can be fetched from the associated symbol
+            var prop = symbol.AssociatedSymbol as IPropertySymbol;
+            if (prop != null)
+                return prop;
 
-                // But for properties/indexers that implement explicit interfaces, Roslyn
-                // does not properly populate `AssociatedSymbol`
-                var props = symbol.ContainingType.GetMembers().OfType<IPropertySymbol>();
-                props = props.Where(p => SymbolEqualityComparer.Default.Equals(symbol, p.GetMethod) || SymbolEqualityComparer.Default.Equals(symbol, p.SetMethod));
-                return props.SingleOrDefault();
-            }
+            // But for properties/indexers that implement explicit interfaces, Roslyn
+            // does not properly populate `AssociatedSymbol`
+            var props = symbol.ContainingType.GetMembers().OfType<IPropertySymbol>();
+            props = props.Where(p => SymbolEqualityComparer.Default.Equals(symbol, p.GetMethod) || SymbolEqualityComparer.Default.Equals(symbol, p.SetMethod));
+            return props.SingleOrDefault();
         }
 
+        /// <summary>
+        /// Gets the property symbol associated with this accessor.
+        /// </summary>
+        IPropertySymbol PropertySymbol => GetPropertySymbol(symbol);
+
         public new Accessor OriginalDefinition => Create(Context, symbol.OriginalDefinition);
 
         public override void Populate(TextWriter trapFile)
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Method.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Method.cs
@@ -240,7 +240,7 @@ public static Method Create(Context cx, IMethodSymbol methodDecl)
                     return Destructor.Create(cx, methodDecl);
                 case MethodKind.PropertyGet:
                 case MethodKind.PropertySet:
-                    return methodDecl.AssociatedSymbol is null ? OrdinaryMethod.Create(cx, methodDecl) : (Method)Accessor.Create(cx, methodDecl);
+                    return Accessor.GetPropertySymbol(methodDecl) is null ? OrdinaryMethod.Create(cx, methodDecl) : (Method)Accessor.Create(cx, methodDecl);
                 case MethodKind.EventAdd:
                 case MethodKind.EventRemove:
                     return EventAccessor.Create(cx, methodDecl);
diff --git a/csharp/ql/test/library-tests/indexers/Indexers12.expected b/csharp/ql/test/library-tests/indexers/Indexers12.expected
@@ -0,0 +1 @@
+| Item[int] | get_Item(int) |
diff --git a/csharp/ql/test/library-tests/indexers/Indexers12.ql b/csharp/ql/test/library-tests/indexers/Indexers12.ql
@@ -0,0 +1,8 @@
+import csharp
+
+from Indexer i, Accessor a, string s
+where
+  i.getDeclaringType().hasQualifiedName("System", s) and
+  s.regexpMatch("Tuple<,*>") and
+  a = i.getAnAccessor()
+select i.toStringWithTypes(), a.toStringWithTypes()
