C#: Allow abstract modifier on interface members

Author: tamasvajk

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

@@ -72,15 +72,11 @@ public static void HasModifier(Context cx, TextWriter trapFile, IEntity target,
 
         public static void ExtractModifiers(Context cx, TextWriter trapFile, IEntity key, ISymbol symbol)
         {
-            var interfaceDefinition = symbol.ContainingType is not null
-                && symbol.ContainingType.Kind == SymbolKind.NamedType
-                && symbol.ContainingType.TypeKind == TypeKind.Interface;
-
             HasAccessibility(cx, trapFile, key, symbol.DeclaredAccessibility);
             if (symbol.Kind == SymbolKind.ErrorType)
                 trapFile.has_modifiers(key, Modifier.Create(cx, Accessibility.Public));
 
-            if (symbol.IsAbstract && (symbol.Kind != SymbolKind.NamedType || ((INamedTypeSymbol)symbol).TypeKind != TypeKind.Interface) && !interfaceDefinition)
+            if (symbol.IsAbstract && (symbol.Kind != SymbolKind.NamedType || ((INamedTypeSymbol)symbol).TypeKind != TypeKind.Interface))
                 HasModifier(cx, trapFile, key, "abstract");
 
             if (symbol.IsSealed)
@@ -94,10 +90,6 @@ public static void ExtractModifiers(Context cx, TextWriter trapFile, IEntity key
             if (symbol.IsVirtual)
                 HasModifier(cx, trapFile, key, "virtual");
 
-            // For some reason, method in interfaces are "virtual", not "abstract"
-            if (symbol.IsAbstract && interfaceDefinition)
-                HasModifier(cx, trapFile, key, "virtual");
-
             if (symbol.Kind == SymbolKind.Field && ((IFieldSymbol)symbol).IsReadOnly)
                 HasModifier(cx, trapFile, key, "readonly");
 

csharp/ql/test/library-tests/modifiers/Modifiers.expected

@@ -45,7 +45,7 @@
 | Modifiers.cs:57:30:57:32 | get_P3 | file://:0:0:0:0 | private |
 | Modifiers.cs:57:47:57:49 | set_P3 | file://:0:0:0:0 | private |
 | Modifiers.cs:60:22:60:23 | I1 | file://:0:0:0:0 | public |
+| Modifiers.cs:62:14:62:15 | M1 | file://:0:0:0:0 | abstract |
 | Modifiers.cs:62:14:62:15 | M1 | file://:0:0:0:0 | public |
-| Modifiers.cs:62:14:62:15 | M1 | file://:0:0:0:0 | virtual |
 | Modifiers.cs:63:14:63:15 | M2 | file://:0:0:0:0 | public |
 | Modifiers.cs:63:14:63:15 | M2 | file://:0:0:0:0 | virtual |