Merge pull request #5197 from tamasvajk/feature/refactor-4

C#: Enable nullability in Extraction.CSharp

csharp/extractor/Semmle.Extraction.CIL/Analyser.cs

@@ -7,7 +7,7 @@ namespace Semmle.Extraction.CIL
 {
     public static class Analyser
     {
-        private static void ExtractCIL(Extractor extractor, TrapWriter trapWriter, bool extractPdbs)
+        private static void ExtractCIL(TracingExtractor extractor, TrapWriter trapWriter, bool extractPdbs)
         {
             using var cilContext = new Context(extractor, trapWriter, extractor.OutputPath, extractPdbs);
             cilContext.Populate(new Assembly(cilContext));
@@ -33,7 +33,7 @@ namespace Semmle.Extraction.CIL
             {
                 var canonicalPathCache = CanonicalPathCache.Create(logger, 1000);
                 var pathTransformer = new PathTransformer(canonicalPathCache);
-                var extractor = new Extractor(false, assemblyPath, logger, pathTransformer);
+                var extractor = new TracingExtractor(assemblyPath, logger, pathTransformer);
                 var transformedAssemblyPath = pathTransformer.Transform(assemblyPath);
                 var project = layout.LookupProjectOrDefault(transformedAssemblyPath);
                 using var trapWriter = project.CreateTrapWriter(logger, transformedAssemblyPath.WithSuffix(".cil"), trapCompression, discardDuplicates: true);

csharp/extractor/Semmle.Extraction.CIL/Context.Factories.cs

@@ -114,7 +114,7 @@ namespace Semmle.Extraction.CIL
                     entity = new MethodSpecificationMethod(gc, (MethodSpecificationHandle)handle);
                     break;
                 case HandleKind.FieldDefinition:
-                    entity = new DefinitionField(gc.Cx, (FieldDefinitionHandle)handle);
+                    entity = new DefinitionField(gc.Context, (FieldDefinitionHandle)handle);
                     break;
                 case HandleKind.TypeReference:
                     var tr = new TypeReferenceType(this, (TypeReferenceHandle)handle);
@@ -130,7 +130,7 @@ namespace Semmle.Extraction.CIL
                     break;
                 case HandleKind.StandaloneSignature:
                     var signature = MdReader.GetStandaloneSignature((StandaloneSignatureHandle)handle);
-                    var method = signature.DecodeMethodSignature(gc.Cx.TypeSignatureDecoder, gc);
+                    var method = signature.DecodeMethodSignature(gc.Context.TypeSignatureDecoder, gc);
                     entity = new FunctionPointerType(this, method);
                     break;
                 default:

csharp/extractor/Semmle.Extraction.CIL/EmptyContext.cs

@@ -9,10 +9,10 @@ namespace Semmle.Extraction.CIL
     {
         public EmptyContext(Context cx)
         {
-            Cx = cx;
+            Context = cx;
         }
 
-        public Context Cx { get; }
+        public Context Context { get; }
 
         public IEnumerable<Entities.Type> TypeParameters { get { yield break; } }
 

csharp/extractor/Semmle.Extraction.CIL/Entities/ArrayType.cs

@@ -42,7 +42,7 @@ namespace Semmle.Extraction.CIL.Entities
 
         public override string Name => elementType.Name + "[]";
 
-        public override Namespace ContainingNamespace => Cx.SystemNamespace;
+        public override Namespace ContainingNamespace => Context.SystemNamespace;
 
         public override Type? ContainingType => null;
 
@@ -50,9 +50,9 @@ namespace Semmle.Extraction.CIL.Entities
 
         public override CilTypeKind Kind => CilTypeKind.Array;
 
-        public override Type Construct(IEnumerable<Type> typeArguments) => Cx.Populate(new ArrayType(Cx, elementType.Construct(typeArguments)));
+        public override Type Construct(IEnumerable<Type> typeArguments) => Context.Populate(new ArrayType(Context, elementType.Construct(typeArguments)));
 
-        public override Type SourceDeclaration => Cx.Populate(new ArrayType(Cx, elementType.SourceDeclaration));
+        public override Type SourceDeclaration => Context.Populate(new ArrayType(Context, elementType.SourceDeclaration));
 
         public override IEnumerable<IExtractionProduct> Contents
         {

csharp/extractor/Semmle.Extraction.CIL/Entities/Assembly.cs

@@ -36,7 +36,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             trapFile.Write(FullName);
             trapFile.Write("#file:///");
-            trapFile.Write(Cx.AssemblyPath.Replace("\\", "/"));
+            trapFile.Write(Context.AssemblyPath.Replace("\\", "/"));
             trapFile.Write(";assembly");
         }
 
@@ -56,24 +56,24 @@ namespace Semmle.Extraction.CIL.Entities
                 yield return file;
                 yield return Tuples.assemblies(this, file, FullName, assemblyName.Name ?? string.Empty, assemblyName.Version?.ToString() ?? string.Empty);
 
-                if (Cx.Pdb != null)
+                if (Context.Pdb != null)
                 {
-                    foreach (var f in Cx.Pdb.SourceFiles)
+                    foreach (var f in Context.Pdb.SourceFiles)
                     {
-                        yield return Cx.CreateSourceFile(f);
+                        yield return Context.CreateSourceFile(f);
                     }
                 }
 
-                foreach (var handle in Cx.MdReader.TypeDefinitions)
+                foreach (var handle in Context.MdReader.TypeDefinitions)
                 {
                     IExtractionProduct? product = null;
                     try
                     {
-                        product = Cx.Create(handle);
+                        product = Context.Create(handle);
                     }
                     catch (InternalError e)
                     {
-                        Cx.ExtractionError("Error processing type definition", e.Message, GeneratedLocation.Create(Cx), e.StackTrace);
+                        Context.ExtractionError("Error processing type definition", e.Message, GeneratedLocation.Create(Context), e.StackTrace);
                     }
 
                     // Limitation of C#: Cannot yield return inside a try-catch.
@@ -81,16 +81,16 @@ namespace Semmle.Extraction.CIL.Entities
                         yield return product;
                 }
 
-                foreach (var handle in Cx.MdReader.MethodDefinitions)
+                foreach (var handle in Context.MdReader.MethodDefinitions)
                 {
                     IExtractionProduct? product = null;
                     try
                     {
-                        product = Cx.Create(handle);
+                        product = Context.Create(handle);
                     }
                     catch (InternalError e)
                     {
-                        Cx.ExtractionError("Error processing bytecode", e.Message, GeneratedLocation.Create(Cx), e.StackTrace);
+                        Context.ExtractionError("Error processing bytecode", e.Message, GeneratedLocation.Create(Context), e.StackTrace);
                     }
 
                     if (product != null)

csharp/extractor/Semmle.Extraction.CIL/Entities/Attribute.cs

@@ -32,7 +32,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             get
             {
-                var constructor = (Method)Cx.Create(attrib.Constructor);
+                var constructor = (Method)Context.Create(attrib.Constructor);
                 yield return constructor;
 
                 yield return Tuples.cil_attribute(this, @object, constructor);
@@ -41,11 +41,11 @@ namespace Semmle.Extraction.CIL.Entities
 
                 try
                 {
-                    decoded = attrib.DecodeValue(new CustomAttributeDecoder(Cx));
+                    decoded = attrib.DecodeValue(new CustomAttributeDecoder(Context));
                 }
                 catch
                 {
-                    Cx.Extractor.Logger.Log(Util.Logging.Severity.Info,
+                    Context.Extractor.Logger.Log(Util.Logging.Severity.Info,
                         $"Attribute decoding is partial. Decoding attribute {constructor.DeclaringType.GetQualifiedName()} failed on {@object}.");
                     yield break;
                 }

csharp/extractor/Semmle.Extraction.CIL/Entities/Base/IGenericContext.cs

@@ -8,7 +8,7 @@ namespace Semmle.Extraction.CIL
     /// </summary>
     internal interface IGenericContext
     {
-        Context Cx { get; }
+        Context Context { get; }
 
         /// <summary>
         /// The list of generic type parameters/arguments, including type parameters/arguments of

csharp/extractor/Semmle.Extraction.CIL/Entities/Base/LabelledEntity.cs

@@ -10,8 +10,7 @@ namespace Semmle.Extraction.CIL
     /// </summary>
     internal abstract class LabelledEntity : Extraction.LabelledEntity, IExtractedEntity
     {
-        // todo: with .NET 5 this can override the base context, and change the return type.
-        public Context Cx => (Context)base.Context;
+        public override Context Context => (Context)base.Context;
 
         protected LabelledEntity(Context cx) : base(cx)
         {

csharp/extractor/Semmle.Extraction.CIL/Entities/Base/UnlabelledEntity.cs

@@ -9,8 +9,7 @@ namespace Semmle.Extraction.CIL
     /// </summary>
     internal abstract class UnlabelledEntity : Extraction.UnlabelledEntity, IExtractedEntity
     {
-        // todo: with .NET 5 this can override the base context, and change the return type.
-        public Context Cx => (Context)base.Context;
+        public override Context Context => (Context)base.Context;
 
         protected UnlabelledEntity(Context cx) : base(cx)
         {

csharp/extractor/Semmle.Extraction.CIL/Entities/DefinitionField.cs

@@ -14,7 +14,7 @@ namespace Semmle.Extraction.CIL.Entities
         public DefinitionField(Context cx, FieldDefinitionHandle handle) : base(cx)
         {
             this.handle = handle;
-            fd = Cx.MdReader.GetFieldDefinition(handle);
+            fd = Context.MdReader.GetFieldDefinition(handle);
         }
 
         public override bool Equals(object? obj)
@@ -28,7 +28,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             get
             {
-                yield return Tuples.metadata_handle(this, Cx.Assembly, MetadataTokens.GetToken(handle));
+                yield return Tuples.metadata_handle(this, Context.Assembly, MetadataTokens.GetToken(handle));
 
                 foreach (var c in base.Contents)
                     yield return c;
@@ -48,16 +48,16 @@ namespace Semmle.Extraction.CIL.Entities
                 if (fd.Attributes.HasFlag(FieldAttributes.Assembly))
                     yield return Tuples.cil_internal(this);
 
-                foreach (var c in Attribute.Populate(Cx, this, fd.GetCustomAttributes()))
+                foreach (var c in Attribute.Populate(Context, this, fd.GetCustomAttributes()))
                     yield return c;
             }
         }
 
-        public override string Name => Cx.GetString(fd.Name);
+        public override string Name => Context.GetString(fd.Name);
 
-        public override Type DeclaringType => (Type)Cx.Create(fd.GetDeclaringType());
+        public override Type DeclaringType => (Type)Context.Create(fd.GetDeclaringType());
 
-        public override Type Type => fd.DecodeSignature(Cx.TypeSignatureDecoder, DeclaringType);
+        public override Type Type => fd.DecodeSignature(Context.TypeSignatureDecoder, DeclaringType);
 
         public override IEnumerable<Type> TypeParameters => throw new NotImplementedException();
 

csharp/extractor/Semmle.Extraction.CIL/Entities/DefinitionMethod.cs

@@ -25,16 +25,16 @@ namespace Semmle.Extraction.CIL.Entities
 
         public DefinitionMethod(IGenericContext gc, MethodDefinitionHandle handle) : base(gc)
         {
-            md = Cx.MdReader.GetMethodDefinition(handle);
+            md = Context.MdReader.GetMethodDefinition(handle);
             this.gc = gc;
             this.handle = handle;
-            name = Cx.GetString(md.Name);
+            name = Context.GetString(md.Name);
 
-            declaringType = (Type)Cx.CreateGeneric(this, md.GetDeclaringType());
+            declaringType = (Type)Context.CreateGeneric(this, md.GetDeclaringType());
 
             signature = md.DecodeSignature(new SignatureDecoder(), this);
 
-            methodDebugInformation = Cx.GetMethodDebugInformation(handle);
+            methodDebugInformation = Context.GetMethodDebugInformation(handle);
         }
 
         public override bool Equals(object? obj)
@@ -48,7 +48,7 @@ namespace Semmle.Extraction.CIL.Entities
 
         public override Type DeclaringType => declaringType;
 
-        public override string Name => Cx.ShortName(md.Name);
+        public override string Name => Context.ShortName(md.Name);
 
         public override string NameLabel => name;
 
@@ -67,14 +67,14 @@ namespace Semmle.Extraction.CIL.Entities
                     // depend on other type parameters (as a constraint).
                     genericParams = new MethodTypeParameter[md.GetGenericParameters().Count];
                     for (var i = 0; i < genericParams.Length; ++i)
-                        genericParams[i] = Cx.Populate(new MethodTypeParameter(this, this, i));
+                        genericParams[i] = Context.Populate(new MethodTypeParameter(this, this, i));
                     for (var i = 0; i < genericParams.Length; ++i)
                         genericParams[i].PopulateHandle(md.GetGenericParameters()[i]);
                     foreach (var p in genericParams)
                         yield return p;
                 }
 
-                var typeSignature = md.DecodeSignature(Cx.TypeSignatureDecoder, this);
+                var typeSignature = md.DecodeSignature(Context.TypeSignatureDecoder, this);
 
                 var parameters = GetParameterExtractionProducts(typeSignature.ParameterTypes).ToArray();
                 Parameters = parameters.OfType<Parameter>().ToArray();
@@ -85,17 +85,17 @@ namespace Semmle.Extraction.CIL.Entities
                 foreach (var c in PopulateFlags)
                     yield return c;
 
-                foreach (var p in md.GetParameters().Select(h => Cx.MdReader.GetParameter(h)).Where(p => p.SequenceNumber > 0))
+                foreach (var p in md.GetParameters().Select(h => Context.MdReader.GetParameter(h)).Where(p => p.SequenceNumber > 0))
                 {
                     var pe = Parameters[IsStatic ? p.SequenceNumber - 1 : p.SequenceNumber];
                     if (p.Attributes.HasFlag(ParameterAttributes.Out))
                         yield return Tuples.cil_parameter_out(pe);
                     if (p.Attributes.HasFlag(ParameterAttributes.In))
                         yield return Tuples.cil_parameter_in(pe);
-                    Attribute.Populate(Cx, pe, p.GetCustomAttributes());
+                    Attribute.Populate(Context, pe, p.GetCustomAttributes());
                 }
 
-                yield return Tuples.metadata_handle(this, Cx.Assembly, MetadataTokens.GetToken(handle));
+                yield return Tuples.metadata_handle(this, Context.Assembly, MetadataTokens.GetToken(handle));
 
                 foreach (var m in GetMethodExtractionProducts(Name, declaringType, typeSignature.ReturnType))
                 {
@@ -103,19 +103,19 @@ namespace Semmle.Extraction.CIL.Entities
                 }
 
                 yield return Tuples.cil_method_source_declaration(this, this);
-                yield return Tuples.cil_method_location(this, Cx.Assembly);
+                yield return Tuples.cil_method_location(this, Context.Assembly);
 
                 if (HasBytecode)
                 {
                     Implementation = new MethodImplementation(this);
                     yield return Implementation;
 
-                    var body = Cx.PeReader.GetMethodBody(md.RelativeVirtualAddress);
+                    var body = Context.PeReader.GetMethodBody(md.RelativeVirtualAddress);
 
                     if (!body.LocalSignature.IsNil)
                     {
-                        var locals = Cx.MdReader.GetStandaloneSignature(body.LocalSignature);
-                        var localVariableTypes = locals.DecodeLocalSignature(Cx.TypeSignatureDecoder, this);
+                        var locals = Context.MdReader.GetStandaloneSignature(body.LocalSignature);
+                        var localVariableTypes = locals.DecodeLocalSignature(Context.TypeSignatureDecoder, this);
 
                         this.locals = new LocalVariable[localVariableTypes.Length];
 
@@ -125,13 +125,13 @@ namespace Semmle.Extraction.CIL.Entities
                             if (t is ByRefType brt)
                             {
                                 t = brt.ElementType;
-                                this.locals[l] = Cx.Populate(new LocalVariable(Cx, Implementation, l, t));
+                                this.locals[l] = Context.Populate(new LocalVariable(Context, Implementation, l, t));
                                 yield return this.locals[l];
                                 yield return Tuples.cil_type_annotation(this.locals[l], TypeAnnotation.Ref);
                             }
                             else
                             {
-                                this.locals[l] = Cx.Populate(new LocalVariable(Cx, Implementation, l, t));
+                                this.locals[l] = Context.Populate(new LocalVariable(Context, Implementation, l, t));
                                 yield return this.locals[l];
                             }
                         }
@@ -152,7 +152,7 @@ namespace Semmle.Extraction.CIL.Entities
 
                     if (methodDebugInformation != null)
                     {
-                        var sourceLocation = Cx.CreateSourceLocation(methodDebugInformation.Location);
+                        var sourceLocation = Context.CreateSourceLocation(methodDebugInformation.Location);
                         yield return sourceLocation;
                         yield return Tuples.cil_method_location(this, sourceLocation);
                     }
@@ -191,7 +191,7 @@ namespace Semmle.Extraction.CIL.Entities
                     yield return Tuples.cil_newslot(this);
 
                 // Populate attributes
-                Attribute.Populate(Cx, this, md.GetCustomAttributes());
+                Attribute.Populate(Context, this, md.GetCustomAttributes());
             }
         }
 
@@ -210,7 +210,7 @@ namespace Semmle.Extraction.CIL.Entities
                 nextSequencePoint = methodDebugInformation.SequencePoints.GetEnumerator();
                 if (nextSequencePoint.MoveNext())
                 {
-                    instructionLocation = Cx.CreateSourceLocation(nextSequencePoint.Current.Location);
+                    instructionLocation = Context.CreateSourceLocation(nextSequencePoint.Current.Location);
                     yield return instructionLocation;
                 }
                 else
@@ -222,12 +222,12 @@ namespace Semmle.Extraction.CIL.Entities
             var child = 0;
             for (var offset = 0; offset < (ilbytes?.Length ?? 0);)
             {
-                var instruction = new Instruction(Cx, this, ilbytes!, offset, child++);
+                var instruction = new Instruction(Context, this, ilbytes!, offset, child++);
                 yield return instruction;
 
                 if (nextSequencePoint != null && offset >= nextSequencePoint.Current.Offset)
                 {
-                    instructionLocation = Cx.CreateSourceLocation(nextSequencePoint.Current.Location);
+                    instructionLocation = Context.CreateSourceLocation(nextSequencePoint.Current.Location);
                     yield return instructionLocation;
                     if (!nextSequencePoint.MoveNext())
                         nextSequencePoint = null;
@@ -257,7 +257,7 @@ namespace Semmle.Extraction.CIL.Entities
             {
                 if (md.ImplAttributes == MethodImplAttributes.IL && md.RelativeVirtualAddress != 0)
                 {
-                    var body = Cx.PeReader.GetMethodBody(md.RelativeVirtualAddress);
+                    var body = Context.PeReader.GetMethodBody(md.RelativeVirtualAddress);
 
                     var ilbytes = body.GetILBytes();
 
@@ -267,7 +267,7 @@ namespace Semmle.Extraction.CIL.Entities
                         Instruction decoded;
                         try
                         {
-                            decoded = new Instruction(Cx, this, ilbytes!, offset, child++);
+                            decoded = new Instruction(Context, this, ilbytes!, offset, child++);
                             offset += decoded.Width;
                         }
                         catch  // lgtm[cs/catch-of-all-exceptions]

csharp/extractor/Semmle.Extraction.CIL/Entities/ErrorType.cs

@@ -16,7 +16,7 @@ namespace Semmle.Extraction.CIL.Entities
 
         public override string Name => "!error";
 
-        public override Namespace ContainingNamespace => Cx.GlobalNamespace;
+        public override Namespace ContainingNamespace => Context.GlobalNamespace;
 
         public override Type? ContainingType => null;
 

csharp/extractor/Semmle.Extraction.CIL/Entities/Event.cs

@@ -24,7 +24,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             parent.WriteId(trapFile);
             trapFile.Write('.');
-            trapFile.Write(Cx.ShortName(ed.Name));
+            trapFile.Write(Context.ShortName(ed.Name));
             trapFile.Write(";cil-event");
         }
 
@@ -39,34 +39,34 @@ namespace Semmle.Extraction.CIL.Entities
         {
             get
             {
-                var signature = (Type)Cx.CreateGeneric(parent, ed.Type);
+                var signature = (Type)Context.CreateGeneric(parent, ed.Type);
                 yield return signature;
 
-                yield return Tuples.cil_event(this, parent, Cx.ShortName(ed.Name), signature);
+                yield return Tuples.cil_event(this, parent, Context.ShortName(ed.Name), signature);
 
                 var accessors = ed.GetAccessors();
                 if (!accessors.Adder.IsNil)
                 {
-                    var adder = (Method)Cx.CreateGeneric(parent, accessors.Adder);
+                    var adder = (Method)Context.CreateGeneric(parent, accessors.Adder);
                     yield return adder;
                     yield return Tuples.cil_adder(this, adder);
                 }
 
                 if (!accessors.Remover.IsNil)
                 {
-                    var remover = (Method)Cx.CreateGeneric(parent, accessors.Remover);
+                    var remover = (Method)Context.CreateGeneric(parent, accessors.Remover);
                     yield return remover;
                     yield return Tuples.cil_remover(this, remover);
                 }
 
                 if (!accessors.Raiser.IsNil)
                 {
-                    var raiser = (Method)Cx.CreateGeneric(parent, accessors.Raiser);
+                    var raiser = (Method)Context.CreateGeneric(parent, accessors.Raiser);
                     yield return raiser;
                     yield return Tuples.cil_raiser(this, raiser);
                 }
 
-                foreach (var c in Attribute.Populate(Cx, this, ed.GetCustomAttributes()))
+                foreach (var c in Attribute.Populate(Context, this, ed.GetCustomAttributes()))
                     yield return c;
             }
         }

csharp/extractor/Semmle.Extraction.CIL/Entities/ExceptionRegion.cs

@@ -13,7 +13,7 @@ namespace Semmle.Extraction.CIL.Entities
         private readonly System.Reflection.Metadata.ExceptionRegion r;
         private readonly Dictionary<int, Instruction> jump_table;
 
-        public ExceptionRegion(IGenericContext gc, MethodImplementation method, int index, System.Reflection.Metadata.ExceptionRegion r, Dictionary<int, Instruction> jump_table) : base(gc.Cx)
+        public ExceptionRegion(IGenericContext gc, MethodImplementation method, int index, System.Reflection.Metadata.ExceptionRegion r, Dictionary<int, Instruction> jump_table) : base(gc.Context)
         {
             this.gc = gc;
             this.method = method;
@@ -46,7 +46,7 @@ namespace Semmle.Extraction.CIL.Entities
 
                 if (!r.CatchType.IsNil)
                 {
-                    var catchType = (Type)Cx.CreateGeneric(gc, r.CatchType);
+                    var catchType = (Type)Context.CreateGeneric(gc, r.CatchType);
                     yield return catchType;
                     yield return Tuples.cil_handler_type(this, catchType);
                 }

csharp/extractor/Semmle.Extraction.CIL/Entities/File.cs

@@ -11,7 +11,7 @@ namespace Semmle.Extraction.CIL.Entities
         public File(Context cx, string path) : base(cx)
         {
             this.OriginalPath = path;
-            TransformedPath = Cx.Extractor.PathTransformer.Transform(OriginalPath);
+            TransformedPath = Context.Extractor.PathTransformer.Transform(OriginalPath);
         }
 
         public override void WriteId(TextWriter trapFile)
@@ -33,7 +33,7 @@ namespace Semmle.Extraction.CIL.Entities
             {
                 if (TransformedPath.ParentDirectory is PathTransformer.ITransformedPath dir)
                 {
-                    var parent = Cx.CreateFolder(dir);
+                    var parent = Context.CreateFolder(dir);
                     yield return parent;
                     yield return Tuples.containerparent(parent, this);
                 }

csharp/extractor/Semmle.Extraction.CIL/Entities/Folder.cs

@@ -24,7 +24,7 @@ namespace Semmle.Extraction.CIL.Entities
             {
                 if (transformedPath.ParentDirectory is PathTransformer.ITransformedPath parent)
                 {
-                    var parentFolder = Cx.CreateFolder(parent);
+                    var parentFolder = Context.CreateFolder(parent);
                     yield return parentFolder;
                     yield return Tuples.containerparent(parentFolder, this);
                 }

csharp/extractor/Semmle.Extraction.CIL/Entities/FunctionPointerType.cs

@@ -30,7 +30,7 @@ namespace Semmle.Extraction.CIL.Entities
             }
         }
 
-        public override Namespace? ContainingNamespace => Cx.GlobalNamespace;
+        public override Namespace? ContainingNamespace => Context.GlobalNamespace;
 
         public override Type? ContainingType => null;
 
@@ -104,7 +104,7 @@ namespace Semmle.Extraction.CIL.Entities
 
                 yield return Tuples.cil_function_pointer_calling_conventions(this, signature.Header.CallingConvention);
 
-                foreach (var p in Method.GetParameterExtractionProducts(signature.ParameterTypes, this, this, Cx, 0))
+                foreach (var p in Method.GetParameterExtractionProducts(signature.ParameterTypes, this, this, Context, 0))
                 {
                     yield return p;
                 }

csharp/extractor/Semmle.Extraction.CIL/Entities/Instruction.cs

@@ -356,7 +356,7 @@ namespace Semmle.Extraction.CIL.Entities
                 switch (PayloadType)
                 {
                     case Payload.String:
-                        yield return Tuples.cil_value(this, Cx.MdReader.GetUserString(MetadataTokens.UserStringHandle(payloadValue)));
+                        yield return Tuples.cil_value(this, Context.MdReader.GetUserString(MetadataTokens.UserStringHandle(payloadValue)));
                         break;
                     case Payload.Float32:
                         yield return Tuples.cil_value(this, BitConverter.ToSingle(data, offset).ToString());
@@ -388,7 +388,7 @@ namespace Semmle.Extraction.CIL.Entities
                         {
                             // A generic EntityHandle.
                             var handle = MetadataTokens.EntityHandle(payloadValue);
-                            var target = Cx.CreateGeneric(Method, handle);
+                            var target = Context.CreateGeneric(Method, handle);
                             yield return target;
                             if (target != null)
                             {
@@ -428,11 +428,11 @@ namespace Semmle.Extraction.CIL.Entities
                             IExtractedEntity? target = null;
                             try
                             {
-                                target = Cx.CreateGeneric(Method, handle);
+                                target = Context.CreateGeneric(Method, handle);
                             }
                             catch (Exception exc)
                             {
-                                Cx.Extractor.Logger.Log(Util.Logging.Severity.Warning, $"Couldn't interpret payload of payload type {PayloadType} as a function pointer type. {exc.Message} {exc.StackTrace}");
+                                Context.Extractor.Logger.Log(Util.Logging.Severity.Warning, $"Couldn't interpret payload of payload type {PayloadType} as a function pointer type. {exc.Message} {exc.StackTrace}");
                             }
 
                             if (target != null)
@@ -501,7 +501,7 @@ namespace Semmle.Extraction.CIL.Entities
                 // TODO: Find a solution to this.
 
                 // For now, just log the error
-                Cx.ExtractionError("A CIL instruction jumps outside the current method", null, Extraction.Entities.GeneratedLocation.Create(Cx), "", Util.Logging.Severity.Warning);
+                Context.ExtractionError("A CIL instruction jumps outside the current method", null, Extraction.Entities.GeneratedLocation.Create(Context), "", Util.Logging.Severity.Warning);
             }
         }
     }

csharp/extractor/Semmle.Extraction.CIL/Entities/MemberReferenceField.cs

@@ -11,12 +11,12 @@ namespace Semmle.Extraction.CIL.Entities
         private readonly IGenericContext gc;
         private readonly Type declType;
 
-        public MemberReferenceField(IGenericContext gc, MemberReferenceHandle handle) : base(gc.Cx)
+        public MemberReferenceField(IGenericContext gc, MemberReferenceHandle handle) : base(gc.Context)
         {
             this.handle = handle;
             this.gc = gc;
-            mr = Cx.MdReader.GetMemberReference(handle);
-            declType = (Type)Cx.CreateGeneric(gc, mr.Parent);
+            mr = Context.MdReader.GetMemberReference(handle);
+            declType = (Type)Context.CreateGeneric(gc, mr.Parent);
         }
 
         public override bool Equals(object? obj)
@@ -29,11 +29,11 @@ namespace Semmle.Extraction.CIL.Entities
             return handle.GetHashCode();
         }
 
-        public override string Name => Cx.GetString(mr.Name);
+        public override string Name => Context.GetString(mr.Name);
 
         public override Type DeclaringType => declType;
 
-        public override Type Type => mr.DecodeFieldSignature(Cx.TypeSignatureDecoder, this);
+        public override Type Type => mr.DecodeFieldSignature(Context.TypeSignatureDecoder, this);
 
         public override IEnumerable<Type> TypeParameters => gc.TypeParameters.Concat(declType.TypeParameters);
 

csharp/extractor/Semmle.Extraction.CIL/Entities/MemberReferenceMethod.cs

@@ -19,11 +19,11 @@ namespace Semmle.Extraction.CIL.Entities
         {
             this.handle = handle;
             this.gc = gc;
-            mr = Cx.MdReader.GetMemberReference(handle);
+            mr = Context.MdReader.GetMemberReference(handle);
 
             signature = mr.DecodeMethodSignature(new SignatureDecoder(), gc);
 
-            parent = (IGenericContext)Cx.CreateGeneric(gc, mr.Parent);
+            parent = (IGenericContext)Context.CreateGeneric(gc, mr.Parent);
 
             var declType = parent is Method parentMethod
                 ? parentMethod.DeclaringType
@@ -33,7 +33,7 @@ namespace Semmle.Extraction.CIL.Entities
                 throw new InternalError("Parent context of method is not a type");
 
             declaringType = declType;
-            nameLabel = Cx.GetString(mr.Name);
+            nameLabel = Context.GetString(mr.Name);
 
             var typeSourceDeclaration = declaringType.SourceDeclaration;
             sourceDeclaration = typeSourceDeclaration == declaringType ? (Method)this : typeSourceDeclaration.LookupMethod(mr.Name, mr.Signature);
@@ -59,7 +59,7 @@ namespace Semmle.Extraction.CIL.Entities
 
         public override Type DeclaringType => declaringType;
 
-        public override string Name => Cx.ShortName(mr.Name);
+        public override string Name => Context.ShortName(mr.Name);
 
         public override IEnumerable<Type> TypeParameters => parent.TypeParameters.Concat(gc.TypeParameters);
 
@@ -69,12 +69,12 @@ namespace Semmle.Extraction.CIL.Entities
             {
                 genericParams = new MethodTypeParameter[signature.GenericParameterCount];
                 for (var p = 0; p < genericParams.Length; ++p)
-                    genericParams[p] = Cx.Populate(new MethodTypeParameter(this, this, p));
+                    genericParams[p] = Context.Populate(new MethodTypeParameter(this, this, p));
 
                 foreach (var p in genericParams)
                     yield return p;
 
-                var typeSignature = mr.DecodeMethodSignature(Cx.TypeSignatureDecoder, this);
+                var typeSignature = mr.DecodeMethodSignature(Context.TypeSignatureDecoder, this);
 
                 var parameters = GetParameterExtractionProducts(typeSignature.ParameterTypes).ToArray();
                 Parameters = parameters.OfType<Parameter>().ToArray();

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

@@ -15,7 +15,7 @@ namespace Semmle.Extraction.CIL.Entities
         protected IGenericContext gc;
         protected MethodSignature<ITypeSignature> signature;
 
-        protected Method(IGenericContext gc) : base(gc.Cx)
+        protected Method(IGenericContext gc) : base(gc.Context)
         {
             this.gc = gc;
         }
@@ -83,10 +83,10 @@ namespace Semmle.Extraction.CIL.Entities
 
             if (!IsStatic)
             {
-                yield return Cx.Populate(new Parameter(Cx, this, i++, DeclaringType));
+                yield return Context.Populate(new Parameter(Context, this, i++, DeclaringType));
             }
 
-            foreach (var p in GetParameterExtractionProducts(parameterTypes, this, this, Cx, i))
+            foreach (var p in GetParameterExtractionProducts(parameterTypes, this, this, Context, i))
             {
                 yield return p;
             }

csharp/extractor/Semmle.Extraction.CIL/Entities/MethodImplementation.cs

@@ -10,7 +10,7 @@ namespace Semmle.Extraction.CIL.Entities
     {
         private readonly Method m;
 
-        public MethodImplementation(Method m) : base(m.Cx)
+        public MethodImplementation(Method m) : base(m.Context)
         {
             this.m = m;
         }
@@ -19,7 +19,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             get
             {
-                yield return Tuples.cil_method_implementation(this, m, Cx.Assembly);
+                yield return Tuples.cil_method_implementation(this, m, Context.Assembly);
             }
         }
     }

csharp/extractor/Semmle.Extraction.CIL/Entities/MethodSpecificationMethod.cs

@@ -21,9 +21,9 @@ namespace Semmle.Extraction.CIL.Entities
         public MethodSpecificationMethod(IGenericContext gc, MethodSpecificationHandle handle) : base(gc)
         {
             this.handle = handle;
-            ms = Cx.MdReader.GetMethodSpecification(handle);
-            typeParams = ms.DecodeSignature(Cx.TypeSignatureDecoder, gc);
-            unboundMethod = (Method)Cx.CreateGeneric(gc, ms.Method);
+            ms = Context.MdReader.GetMethodSpecification(handle);
+            typeParams = ms.DecodeSignature(Context.TypeSignatureDecoder, gc);
+            unboundMethod = (Method)Context.CreateGeneric(gc, ms.Method);
         }
 
         public override void WriteId(TextWriter trapFile)
@@ -66,12 +66,12 @@ namespace Semmle.Extraction.CIL.Entities
                 switch (ms.Method.Kind)
                 {
                     case HandleKind.MemberReference:
-                        var mr = Cx.MdReader.GetMemberReference((MemberReferenceHandle)ms.Method);
-                        constructedTypeSignature = mr.DecodeMethodSignature(Cx.TypeSignatureDecoder, this);
+                        var mr = Context.MdReader.GetMemberReference((MemberReferenceHandle)ms.Method);
+                        constructedTypeSignature = mr.DecodeMethodSignature(Context.TypeSignatureDecoder, this);
                         break;
                     case HandleKind.MethodDefinition:
-                        var md = Cx.MdReader.GetMethodDefinition((MethodDefinitionHandle)ms.Method);
-                        constructedTypeSignature = md.DecodeSignature(Cx.TypeSignatureDecoder, this);
+                        var md = Context.MdReader.GetMethodDefinition((MethodDefinitionHandle)ms.Method);
+                        constructedTypeSignature = md.DecodeSignature(Context.TypeSignatureDecoder, this);
                         break;
                     default:
                         throw new InternalError($"Unexpected constructed method handle kind {ms.Method.Kind}");

csharp/extractor/Semmle.Extraction.CIL/Entities/NoMetadataHandleType.cs

@@ -38,11 +38,11 @@ namespace Semmle.Extraction.CIL.Entities
 
             unboundGenericType = nameParser.UnboundGenericTypeName == null
                 ? this
-                : new NoMetadataHandleType(Cx, nameParser.UnboundGenericTypeName);
+                : new NoMetadataHandleType(Context, nameParser.UnboundGenericTypeName);
 
             if (nameParser.TypeArguments != null)
             {
-                thisTypeArguments = nameParser.TypeArguments.Select(t => new NoMetadataHandleType(Cx, t)).ToArray();
+                thisTypeArguments = nameParser.TypeArguments.Select(t => new NoMetadataHandleType(Context, t)).ToArray();
             }
             else
             {
@@ -51,14 +51,14 @@ namespace Semmle.Extraction.CIL.Entities
 
             containingType = isContainerNamespace
                 ? null
-                : new NoMetadataHandleType(Cx, containerName);
+                : new NoMetadataHandleType(Context, containerName);
 
             containingNamespace = isContainerNamespace
-                ? containerName == Cx.GlobalNamespace.Name
-                    ? Cx.GlobalNamespace
-                    : containerName == Cx.SystemNamespace.Name
-                        ? Cx.SystemNamespace
-                        : new Namespace(Cx, containerName)
+                ? containerName == Context.GlobalNamespace.Name
+                    ? Context.GlobalNamespace
+                    : containerName == Context.SystemNamespace.Name
+                        ? Context.SystemNamespace
+                        : new Namespace(Context, containerName)
                 : null;
 
             Populate();
@@ -68,10 +68,10 @@ namespace Semmle.Extraction.CIL.Entities
         {
             if (ContainingNamespace is object)
             {
-                Cx.Populate(ContainingNamespace);
+                Context.Populate(ContainingNamespace);
             }
 
-            Cx.Populate(this);
+            Context.Populate(this);
         }
 
         public override bool Equals(object? obj)
@@ -118,7 +118,7 @@ namespace Semmle.Extraction.CIL.Entities
             if (TotalTypeParametersCount != typeArguments.Count())
                 throw new InternalError("Mismatched type arguments");
 
-            return Cx.Populate(new ConstructedType(Cx, this, typeArguments));
+            return Context.Populate(new ConstructedType(Context, this, typeArguments));
         }
 
         public override void WriteAssemblyPrefix(TextWriter trapFile)
@@ -133,7 +133,7 @@ namespace Semmle.Extraction.CIL.Entities
             }
             else
             {
-                Cx.WriteAssemblyPrefix(trapFile);
+                Context.WriteAssemblyPrefix(trapFile);
             }
         }
 

csharp/extractor/Semmle.Extraction.CIL/Entities/PdbSourceFile.cs

@@ -21,9 +21,9 @@ namespace Semmle.Extraction.CIL.Entities
                 var text = file.Contents;
 
                 if (text == null)
-                    Cx.Extractor.Logger.Log(Util.Logging.Severity.Warning, string.Format("PDB source file {0} could not be found", OriginalPath));
+                    Context.Extractor.Logger.Log(Util.Logging.Severity.Warning, string.Format("PDB source file {0} could not be found", OriginalPath));
                 else
-                    Cx.TrapWriter.Archive(TransformedPath, text);
+                    Context.TrapWriter.Archive(TransformedPath, text);
 
                 yield return Tuples.file_extraction_mode(this, 2);
             }

csharp/extractor/Semmle.Extraction.CIL/Entities/PrimitiveType.cs

@@ -27,7 +27,7 @@ namespace Semmle.Extraction.CIL.Entities
 
         public override string Name => typeCode.Id();
 
-        public override Namespace ContainingNamespace => Cx.SystemNamespace;
+        public override Namespace ContainingNamespace => Context.SystemNamespace;
 
         public override Type? ContainingType => null;
 

csharp/extractor/Semmle.Extraction.CIL/Entities/Property.cs

@@ -15,11 +15,11 @@ namespace Semmle.Extraction.CIL.Entities
         private readonly PropertyDefinition pd;
         private readonly IGenericContext gc;
 
-        public Property(IGenericContext gc, Type type, PropertyDefinitionHandle handle) : base(gc.Cx)
+        public Property(IGenericContext gc, Type type, PropertyDefinitionHandle handle) : base(gc.Context)
         {
             this.gc = gc;
             this.handle = handle;
-            pd = Cx.MdReader.GetPropertyDefinition(handle);
+            pd = Context.MdReader.GetPropertyDefinition(handle);
             this.type = type;
         }
 
@@ -27,7 +27,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             trapFile.WriteSubId(type);
             trapFile.Write('.');
-            trapFile.Write(Cx.GetString(pd.Name));
+            trapFile.Write(Context.GetString(pd.Name));
             trapFile.Write("(");
             var index = 0;
             var signature = pd.DecodeSignature(new SignatureDecoder(), gc);
@@ -51,10 +51,10 @@ namespace Semmle.Extraction.CIL.Entities
         {
             get
             {
-                yield return Tuples.metadata_handle(this, Cx.Assembly, MetadataTokens.GetToken(handle));
-                var sig = pd.DecodeSignature(Cx.TypeSignatureDecoder, type);
+                yield return Tuples.metadata_handle(this, Context.Assembly, MetadataTokens.GetToken(handle));
+                var sig = pd.DecodeSignature(Context.TypeSignatureDecoder, type);
 
-                var name = Cx.ShortName(pd.Name);
+                var name = Context.ShortName(pd.Name);
 
                 var t = sig.ReturnType;
                 if (t is ModifiedType mt)
@@ -72,19 +72,19 @@ namespace Semmle.Extraction.CIL.Entities
                 var accessors = pd.GetAccessors();
                 if (!accessors.Getter.IsNil)
                 {
-                    var getter = (Method)Cx.CreateGeneric(type, accessors.Getter);
+                    var getter = (Method)Context.CreateGeneric(type, accessors.Getter);
                     yield return getter;
                     yield return Tuples.cil_getter(this, getter);
                 }
 
                 if (!accessors.Setter.IsNil)
                 {
-                    var setter = (Method)Cx.CreateGeneric(type, accessors.Setter);
+                    var setter = (Method)Context.CreateGeneric(type, accessors.Setter);
                     yield return setter;
                     yield return Tuples.cil_setter(this, setter);
                 }
 
-                foreach (var c in Attribute.Populate(Cx, this, pd.GetCustomAttributes()))
+                foreach (var c in Attribute.Populate(Context, this, pd.GetCustomAttributes()))
                     yield return c;
             }
         }

csharp/extractor/Semmle.Extraction.CIL/Entities/SignatureDecoder.cs

@@ -250,7 +250,7 @@ namespace Semmle.Extraction.CIL.Entities
 
             public void WriteId(TextWriter trapFile, IGenericContext gc)
             {
-                var type = (Type)gc.Cx.Create(handle);
+                var type = (Type)gc.Context.Create(handle);
                 type.WriteId(trapFile);
             }
         }
@@ -271,7 +271,7 @@ namespace Semmle.Extraction.CIL.Entities
 
             public void WriteId(TextWriter trapFile, IGenericContext gc)
             {
-                var type = (Type)gc.Cx.Create(handle);
+                var type = (Type)gc.Context.Create(handle);
                 type.WriteId(trapFile);
             }
         }

csharp/extractor/Semmle.Extraction.CIL/Entities/Type.cs

@@ -174,7 +174,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             if (TryGetPrimitiveTypeCode(out var code))
             {
-                t = Cx.Create(code);
+                t = Context.Create(code);
                 return true;
             }
 
@@ -185,7 +185,7 @@ namespace Semmle.Extraction.CIL.Entities
         private bool TryGetPrimitiveTypeCode(out PrimitiveTypeCode code)
         {
             if (ContainingType == null &&
-                ContainingNamespace?.Name == Cx.SystemNamespace.Name &&
+                ContainingNamespace?.Name == Context.SystemNamespace.Name &&
                 primitiveTypeCodeMapping.TryGetValue(Name, out code))
             {
                 return true;
@@ -200,6 +200,6 @@ namespace Semmle.Extraction.CIL.Entities
         public sealed override IEnumerable<Type> MethodParameters => Enumerable.Empty<Type>();
 
         public static Type DecodeType(IGenericContext gc, TypeSpecificationHandle handle) =>
-            gc.Cx.MdReader.GetTypeSpecification(handle).DecodeSignature(gc.Cx.TypeSignatureDecoder, gc);
+            gc.Context.MdReader.GetTypeSpecification(handle).DecodeSignature(gc.Context.TypeSignatureDecoder, gc);
     }
 }

csharp/extractor/Semmle.Extraction.CIL/Entities/TypeDefinitionType.cs

@@ -45,9 +45,9 @@ namespace Semmle.Extraction.CIL.Entities
             idWriter.WriteId(trapFile, inContext);
         }
 
-        public override string Name => GenericsHelper.GetNonGenericName(td.Name, Cx.MdReader);
+        public override string Name => GenericsHelper.GetNonGenericName(td.Name, Context.MdReader);
 
-        public override Namespace ContainingNamespace => Cx.Create(td.NamespaceDefinition);
+        public override Namespace ContainingNamespace => Context.Create(td.NamespaceDefinition);
 
         public override Type? ContainingType => declType;
 
@@ -58,14 +58,14 @@ namespace Semmle.Extraction.CIL.Entities
             if (TotalTypeParametersCount != typeArguments.Count())
                 throw new InternalError("Mismatched type arguments");
 
-            return Cx.Populate(new ConstructedType(Cx, this, typeArguments));
+            return Context.Populate(new ConstructedType(Context, this, typeArguments));
         }
 
         public override void WriteAssemblyPrefix(TextWriter trapFile)
         {
             var ct = ContainingType;
             if (ct is null)
-                Cx.WriteAssemblyPrefix(trapFile);
+                Context.WriteAssemblyPrefix(trapFile);
             else if (IsPrimitiveType)
                 trapFile.Write(Type.PrimitiveTypePrefix);
             else
@@ -83,7 +83,7 @@ namespace Semmle.Extraction.CIL.Entities
 
             // Two-phase population because type parameters can be mutually dependent
             for (var i = 0; i < newTypeParams.Length; ++i)
-                newTypeParams[i] = Cx.Populate(new TypeTypeParameter(this, i));
+                newTypeParams[i] = Context.Populate(new TypeTypeParameter(this, i));
             for (var i = 0; i < newTypeParams.Length; ++i)
                 newTypeParams[i].PopulateHandle(genericParams[i + toSkip]);
             return newTypeParams;
@@ -96,7 +96,7 @@ namespace Semmle.Extraction.CIL.Entities
                 var containingType = td.GetDeclaringType();
                 var parentTypeParameters = containingType.IsNil
                     ? 0
-                    : Cx.MdReader.GetTypeDefinition(containingType).GetGenericParameters().Count;
+                    : Context.MdReader.GetTypeDefinition(containingType).GetGenericParameters().Count;
 
                 return td.GetGenericParameters().Count - parentTypeParameters;
             }
@@ -110,7 +110,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             get
             {
-                yield return Tuples.metadata_handle(this, Cx.Assembly, MetadataTokens.GetToken(handle));
+                yield return Tuples.metadata_handle(this, Context.Assembly, MetadataTokens.GetToken(handle));
 
                 foreach (var c in base.Contents) yield return c;
 
@@ -119,7 +119,7 @@ namespace Semmle.Extraction.CIL.Entities
                 foreach (var f in td.GetFields())
                 {
                     // Populate field if needed
-                    yield return Cx.CreateGeneric(this, f);
+                    yield return Context.CreateGeneric(this, f);
                 }
 
                 foreach (var prop in td.GetProperties())
@@ -129,16 +129,16 @@ namespace Semmle.Extraction.CIL.Entities
 
                 foreach (var @event in td.GetEvents())
                 {
-                    yield return new Event(Cx, this, @event);
+                    yield return new Event(Context, this, @event);
                 }
 
-                foreach (var a in Attribute.Populate(Cx, this, td.GetCustomAttributes()))
+                foreach (var a in Attribute.Populate(Context, this, td.GetCustomAttributes()))
                     yield return a;
 
-                foreach (var impl in td.GetMethodImplementations().Select(i => Cx.MdReader.GetMethodImplementation(i)))
+                foreach (var impl in td.GetMethodImplementations().Select(i => Context.MdReader.GetMethodImplementation(i)))
                 {
-                    var m = (Method)Cx.CreateGeneric(this, impl.MethodBody);
-                    var decl = (Method)Cx.CreateGeneric(this, impl.MethodDeclaration);
+                    var m = (Method)Context.CreateGeneric(this, impl.MethodBody);
+                    var decl = (Method)Context.CreateGeneric(this, impl.MethodDeclaration);
 
                     yield return m;
                     yield return decl;
@@ -166,7 +166,7 @@ namespace Semmle.Extraction.CIL.Entities
 
                 if (!td.BaseType.IsNil)
                 {
-                    var @base = (Type)Cx.CreateGeneric(this, td.BaseType);
+                    var @base = (Type)Context.CreateGeneric(this, td.BaseType);
                     yield return @base;
                     yield return Tuples.cil_base_class(this, @base);
 
@@ -174,21 +174,21 @@ namespace Semmle.Extraction.CIL.Entities
                         GetUnderlyingEnumType() is var underlying &&
                         underlying.HasValue)
                     {
-                        var underlyingType = Cx.Create(underlying.Value);
+                        var underlyingType = Context.Create(underlying.Value);
                         yield return underlyingType;
                         yield return Tuples.cil_enum_underlying_type(this, underlyingType);
                     }
                 }
 
-                foreach (var @interface in td.GetInterfaceImplementations().Select(i => Cx.MdReader.GetInterfaceImplementation(i)))
+                foreach (var @interface in td.GetInterfaceImplementations().Select(i => Context.MdReader.GetInterfaceImplementation(i)))
                 {
-                    var t = (Type)Cx.CreateGeneric(this, @interface.Interface);
+                    var t = (Type)Context.CreateGeneric(this, @interface.Interface);
                     yield return t;
                     yield return Tuples.cil_base_interface(this, t);
                 }
 
                 // Only type definitions have locations.
-                yield return Tuples.cil_type_location(this, Cx.Assembly);
+                yield return Tuples.cil_type_location(this, Context.Assembly);
             }
         }
 
@@ -204,36 +204,36 @@ namespace Semmle.Extraction.CIL.Entities
 
         private bool IsSystemEnum(TypeReferenceHandle baseType)
         {
-            var baseTypeReference = Cx.MdReader.GetTypeReference(baseType);
+            var baseTypeReference = Context.MdReader.GetTypeReference(baseType);
 
             return IsSystemEnum(baseTypeReference.Name, baseTypeReference.Namespace);
         }
 
         private bool IsSystemEnum(TypeDefinitionHandle baseType)
         {
-            var baseTypeDefinition = Cx.MdReader.GetTypeDefinition(baseType);
+            var baseTypeDefinition = Context.MdReader.GetTypeDefinition(baseType);
 
             return IsSystemEnum(baseTypeDefinition.Name, baseTypeDefinition.Namespace);
         }
 
         private bool IsSystemEnum(StringHandle typeName, StringHandle namespaceName)
         {
-            return Cx.MdReader.StringComparer.Equals(typeName, "Enum") &&
+            return Context.MdReader.StringComparer.Equals(typeName, "Enum") &&
                 !namespaceName.IsNil &&
-                Cx.MdReader.StringComparer.Equals(namespaceName, "System");
+                Context.MdReader.StringComparer.Equals(namespaceName, "System");
         }
 
         internal PrimitiveTypeCode? GetUnderlyingEnumType()
         {
             foreach (var handle in td.GetFields())
             {
-                var field = Cx.MdReader.GetFieldDefinition(handle);
+                var field = Context.MdReader.GetFieldDefinition(handle);
                 if (field.Attributes.HasFlag(FieldAttributes.Static))
                 {
                     continue;
                 }
 
-                var blob = Cx.MdReader.GetBlobReader(field.Signature);
+                var blob = Context.MdReader.GetBlobReader(field.Signature);
                 if (blob.ReadSignatureHeader().Kind != SignatureKind.Field)
                 {
                     break;
@@ -249,11 +249,11 @@ namespace Semmle.Extraction.CIL.Entities
         {
             foreach (var h in td.GetMethods())
             {
-                var md = Cx.MdReader.GetMethodDefinition(h);
+                var md = Context.MdReader.GetMethodDefinition(h);
 
                 if (md.Name == name && md.Signature == signature)
                 {
-                    return (Method)Cx.Create(h);
+                    return (Method)Context.Create(h);
                 }
             }
 

csharp/extractor/Semmle.Extraction.CIL/Entities/TypeParameter.cs

@@ -11,7 +11,7 @@ namespace Semmle.Extraction.CIL.Entities
     {
         protected readonly IGenericContext gc;
 
-        protected TypeParameter(IGenericContext gc) : base(gc.Cx)
+        protected TypeParameter(IGenericContext gc) : base(gc.Context)
         {
             this.gc = gc;
         }
@@ -32,7 +32,7 @@ namespace Semmle.Extraction.CIL.Entities
         {
             if (!parameterHandle.IsNil)
             {
-                var tp = Cx.MdReader.GetGenericParameter(parameterHandle);
+                var tp = Context.MdReader.GetGenericParameter(parameterHandle);
 
                 if (tp.Attributes.HasFlag(GenericParameterAttributes.Contravariant))
                     yield return Tuples.cil_typeparam_contravariant(this);
@@ -45,9 +45,9 @@ namespace Semmle.Extraction.CIL.Entities
                 if (tp.Attributes.HasFlag(GenericParameterAttributes.NotNullableValueTypeConstraint))
                     yield return Tuples.cil_typeparam_struct(this);
 
-                foreach (var constraint in tp.GetConstraints().Select(h => Cx.MdReader.GetGenericParameterConstraint(h)))
+                foreach (var constraint in tp.GetConstraints().Select(h => Context.MdReader.GetGenericParameterConstraint(h)))
                 {
-                    var t = (Type)Cx.CreateGeneric(this.gc, constraint.Type);
+                    var t = (Type)Context.CreateGeneric(this.gc, constraint.Type);
                     yield return t;
                     yield return Tuples.cil_typeparam_constraint(this, t);
                 }

csharp/extractor/Semmle.Extraction.CIL/Entities/TypeReferenceType.cs

@@ -46,16 +46,16 @@ namespace Semmle.Extraction.CIL.Entities
             }
         }
 
-        public override string Name => GenericsHelper.GetNonGenericName(tr.Name, Cx.MdReader);
+        public override string Name => GenericsHelper.GetNonGenericName(tr.Name, Context.MdReader);
 
-        public override Namespace ContainingNamespace => Cx.CreateNamespace(tr.Namespace);
+        public override Namespace ContainingNamespace => Context.CreateNamespace(tr.Namespace);
 
         public override Type? ContainingType
         {
             get
             {
                 return tr.ResolutionScope.Kind == HandleKind.TypeReference
-                    ? (Type)Cx.Create((TypeReferenceHandle)tr.ResolutionScope)
+                    ? (Type)Context.Create((TypeReferenceHandle)tr.ResolutionScope)
                     : null;
             }
         }
@@ -70,19 +70,19 @@ namespace Semmle.Extraction.CIL.Entities
                     ContainingType!.WriteAssemblyPrefix(trapFile);
                     break;
                 case HandleKind.AssemblyReference:
-                    var assemblyDef = Cx.MdReader.GetAssemblyReference((AssemblyReferenceHandle)tr.ResolutionScope);
-                    trapFile.Write(Cx.GetString(assemblyDef.Name));
+                    var assemblyDef = Context.MdReader.GetAssemblyReference((AssemblyReferenceHandle)tr.ResolutionScope);
+                    trapFile.Write(Context.GetString(assemblyDef.Name));
                     trapFile.Write('_');
                     trapFile.Write(assemblyDef.Version.ToString());
                     trapFile.Write(Entities.Type.AssemblyTypeNameSeparator);
                     break;
                 default:
-                    Cx.WriteAssemblyPrefix(trapFile);
+                    Context.WriteAssemblyPrefix(trapFile);
                     break;
             }
         }
 
-        public override int ThisTypeParameterCount => GenericsHelper.GetGenericTypeParameterCount(tr.Name, Cx.MdReader);
+        public override int ThisTypeParameterCount => GenericsHelper.GetGenericTypeParameterCount(tr.Name, Context.MdReader);
 
         public override IEnumerable<Type> TypeParameters => GenericsHelper.GetAllTypeParameters(ContainingType, typeParams!.Value);
 
@@ -98,7 +98,7 @@ namespace Semmle.Extraction.CIL.Entities
             if (TotalTypeParametersCount != typeArguments.Count())
                 throw new InternalError("Mismatched type arguments");
 
-            return Cx.Populate(new ConstructedType(Cx, this, typeArguments));
+            return Context.Populate(new ConstructedType(Context, this, typeArguments));
         }
     }
 }

csharp/extractor/Semmle.Extraction.CSharp/Analyser.cs

@@ -1,573 +0,0 @@
-using System;
-using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.CSharp;
-using System.IO;
-using System.Linq;
-using Semmle.Extraction.CSharp.Populators;
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using System.Diagnostics;
-using Semmle.Util.Logging;
-using Semmle.Util;
-
-namespace Semmle.Extraction.CSharp
-{
-    /// <summary>
-    /// Encapsulates a C# analysis task.
-    /// </summary>
-    public sealed class Analyser : IDisposable
-    {
-        private Extraction.Extractor extractor;
-        private CSharpCompilation compilation;
-        private Layout layout;
-        private bool init;
-        private readonly object progressMutex = new object();
-        private int taskCount = 0;
-        private CommonOptions options;
-        private Entities.Compilation compilationEntity;
-        private IDisposable compilationTrapFile;
-
-        private readonly Stopwatch stopWatch = new Stopwatch();
-
-        private readonly IProgressMonitor progressMonitor;
-
-        public ILogger Logger { get; }
-
-        public bool AddAssemblyTrapPrefix { get; }
-
-        public PathTransformer PathTransformer { get; }
-
-        public Analyser(IProgressMonitor pm, ILogger logger, bool addAssemblyTrapPrefix, PathTransformer pathTransformer)
-        {
-            Logger = logger;
-            AddAssemblyTrapPrefix = addAssemblyTrapPrefix;
-            Logger.Log(Severity.Info, "EXTRACTION STARTING at {0}", DateTime.Now);
-            stopWatch.Start();
-            progressMonitor = pm;
-            PathTransformer = pathTransformer;
-        }
-
-        /// <summary>
-        /// Start initialization of the analyser.
-        /// </summary>
-        /// <param name="roslynArgs">The arguments passed to Roslyn.</param>
-        /// <returns>A Boolean indicating whether to proceed with extraction.</returns>
-        public bool BeginInitialize(IEnumerable<string> roslynArgs)
-        {
-            return init = LogRoslynArgs(roslynArgs, Extraction.Extractor.Version);
-        }
-
-        /// <summary>
-        /// End initialization of the analyser.
-        /// </summary>
-        /// <param name="commandLineArguments">Arguments passed to csc.</param>
-        /// <param name="options">Extractor options.</param>
-        /// <param name="compilation">The Roslyn compilation.</param>
-        /// <returns>A Boolean indicating whether to proceed with extraction.</returns>
-        public void EndInitialize(
-           CSharpCommandLineArguments commandLineArguments,
-           Options options,
-           CSharpCompilation compilation)
-        {
-            if (!init)
-                throw new InternalError("EndInitialize called without BeginInitialize returning true");
-            layout = new Layout();
-            this.options = options;
-            this.compilation = compilation;
-            extractor = new Extraction.Extractor(false, GetOutputName(compilation, commandLineArguments), Logger, PathTransformer);
-            LogDiagnostics();
-
-            SetReferencePaths();
-
-            CompilationErrors += FilteredDiagnostics.Count();
-        }
-
-        /// <summary>
-        ///     Constructs the map from assembly string to its filename.
-        ///
-        ///     Roslyn doesn't record the relationship between a filename and its assembly
-        ///     information, so we need to retrieve this information manually.
-        /// </summary>
-        private void SetReferencePaths()
-        {
-            foreach (var reference in compilation.References.OfType<PortableExecutableReference>())
-            {
-                try
-                {
-                    var refPath = reference.FilePath;
-
-                    /*  This method is significantly faster and more lightweight than using
-                     *  System.Reflection.Assembly.ReflectionOnlyLoadFrom. It is also allows
-                     *  loading the same assembly from different locations.
-                     */
-                    using var pereader = new System.Reflection.PortableExecutable.PEReader(new FileStream(refPath, FileMode.Open, FileAccess.Read, FileShare.Read));
-
-                    var metadata = pereader.GetMetadata();
-                    string assemblyIdentity;
-                    unsafe
-                    {
-                        var reader = new System.Reflection.Metadata.MetadataReader(metadata.Pointer, metadata.Length);
-                        var def = reader.GetAssemblyDefinition();
-                        assemblyIdentity = reader.GetString(def.Name) + " " + def.Version;
-                    }
-                    extractor.SetAssemblyFile(assemblyIdentity, refPath);
-
-                }
-                catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
-                {
-                    extractor.Message(new Message("Exception reading reference file", reference.FilePath, null, ex.StackTrace));
-                }
-            }
-        }
-
-        public void InitializeStandalone(CSharpCompilation compilationIn, CommonOptions options)
-        {
-            compilation = compilationIn;
-            layout = new Layout();
-            extractor = new Extraction.Extractor(true, null, Logger, PathTransformer);
-            this.options = options;
-            LogExtractorInfo(Extraction.Extractor.Version);
-            SetReferencePaths();
-        }
-
-        private readonly HashSet<string> errorsToIgnore = new HashSet<string>
-        {
-            "CS7027",   // Code signing failure
-            "CS1589",   // XML referencing not supported
-            "CS1569"    // Error writing XML documentation
-        };
-
-        private IEnumerable<Diagnostic> FilteredDiagnostics
-        {
-            get
-            {
-                return extractor == null || extractor.Standalone || compilation == null ? Enumerable.Empty<Diagnostic>() :
-                    compilation.
-                    GetDiagnostics().
-                    Where(e => e.Severity >= DiagnosticSeverity.Error && !errorsToIgnore.Contains(e.Id));
-            }
-        }
-
-        public IEnumerable<string> MissingTypes => extractor.MissingTypes;
-
-        public IEnumerable<string> MissingNamespaces => extractor.MissingNamespaces;
-
-        /// <summary>
-        /// Determine the path of the output dll/exe.
-        /// </summary>
-        /// <param name="compilation">Information about the compilation.</param>
-        /// <param name="cancel">Cancellation token required.</param>
-        /// <returns>The filename.</returns>
-        private static string GetOutputName(CSharpCompilation compilation,
-            CSharpCommandLineArguments commandLineArguments)
-        {
-            // There's no apparent way to access the output filename from the compilation,
-            // so we need to re-parse the command line arguments.
-
-            if (commandLineArguments.OutputFileName == null)
-            {
-                // No output specified: Use name based on first filename
-                var entry = compilation.GetEntryPoint(System.Threading.CancellationToken.None);
-                if (entry == null)
-                {
-                    if (compilation.SyntaxTrees.Length == 0)
-                        throw new InvalidOperationException("No source files seen");
-
-                    // Probably invalid, but have a go anyway.
-                    var entryPointFile = compilation.SyntaxTrees.First().FilePath;
-                    return Path.ChangeExtension(entryPointFile, ".exe");
-                }
-
-                var entryPointFilename = entry.Locations.First().SourceTree.FilePath;
-                return Path.ChangeExtension(entryPointFilename, ".exe");
-            }
-
-            return Path.Combine(commandLineArguments.OutputDirectory, commandLineArguments.OutputFileName);
-        }
-
-        /// <summary>
-        /// Perform an analysis on a source file/syntax tree.
-        /// </summary>
-        /// <param name="tree">Syntax tree to analyse.</param>
-        public void AnalyseTree(SyntaxTree tree)
-        {
-            extractionTasks.Add(() => DoExtractTree(tree));
-        }
-
-        /// <summary>
-        /// Perform an analysis on an assembly.
-        /// </summary>
-        /// <param name="assembly">Assembly to analyse.</param>
-        private void AnalyseReferenceAssembly(PortableExecutableReference assembly)
-        {
-            // CIL first - it takes longer.
-            if (options.CIL)
-                extractionTasks.Add(() => DoExtractCIL(assembly));
-            extractionTasks.Add(() => DoAnalyseReferenceAssembly(assembly));
-        }
-
-        private static bool FileIsUpToDate(string src, string dest)
-        {
-            return File.Exists(dest) &&
-                File.GetLastWriteTime(dest) >= File.GetLastWriteTime(src);
-        }
-
-        /// <summary>
-        /// Extracts compilation-wide entities, such as compilations and compiler diagnostics.
-        /// </summary>
-        public void AnalyseCompilation()
-        {
-            extractionTasks.Add(() => DoAnalyseCompilation());
-        }
-
-        private void DoAnalyseCompilation()
-        {
-            try
-            {
-                var assemblyPath = extractor.OutputPath;
-                var transformedAssemblyPath = PathTransformer.Transform(assemblyPath);
-                var assembly = compilation.Assembly;
-                var projectLayout = layout.LookupProjectOrDefault(transformedAssemblyPath);
-                var trapWriter = projectLayout.CreateTrapWriter(Logger, transformedAssemblyPath, options.TrapCompression, discardDuplicates: false);
-                compilationTrapFile = trapWriter;  // Dispose later
-                var cx = new Context(extractor, compilation.Clone(), trapWriter, new AssemblyScope(assembly, assemblyPath), AddAssemblyTrapPrefix);
-
-                compilationEntity = Entities.Compilation.Create(cx);
-            }
-            catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
-            {
-                Logger.Log(Severity.Error, "  Unhandled exception analyzing {0}: {1}", "compilation", ex);
-            }
-        }
-
-        public void LogPerformance(Entities.PerformanceMetrics p) => compilationEntity.PopulatePerformance(p);
-
-        /// <summary>
-        ///     Extract an assembly to a new trap file.
-        ///     If the trap file exists, skip extraction to avoid duplicating
-        ///     extraction within the snapshot.
-        /// </summary>
-        /// <param name="r">The assembly to extract.</param>
-        private void DoAnalyseReferenceAssembly(PortableExecutableReference r)
-        {
-            try
-            {
-                var stopwatch = new Stopwatch();
-                stopwatch.Start();
-
-                var assemblyPath = r.FilePath;
-                var transformedAssemblyPath = PathTransformer.Transform(assemblyPath);
-                var projectLayout = layout.LookupProjectOrDefault(transformedAssemblyPath);
-                using var trapWriter = projectLayout.CreateTrapWriter(Logger, transformedAssemblyPath, options.TrapCompression, discardDuplicates: true);
-
-                var skipExtraction = options.Cache && File.Exists(trapWriter.TrapFile);
-
-                if (!skipExtraction)
-                {
-                    /* Note on parallel builds:
-                     *
-                     * The trap writer and source archiver both perform atomic moves
-                     * of the file to the final destination.
-                     *
-                     * If the same source file or trap file are generated concurrently
-                     * (by different parallel invocations of the extractor), then
-                     * last one wins.
-                     *
-                     * Specifically, if two assemblies are analysed concurrently in a build,
-                     * then there is a small amount of duplicated work but the output should
-                     * still be correct.
-                     */
-
-                    // compilation.Clone() reduces memory footprint by allowing the symbols
-                    // in c to be garbage collected.
-                    Compilation c = compilation.Clone();
-
-
-                    if (c.GetAssemblyOrModuleSymbol(r) is IAssemblySymbol assembly)
-                    {
-                        var cx = new Context(extractor, c, trapWriter, new AssemblyScope(assembly, assemblyPath), AddAssemblyTrapPrefix);
-
-                        foreach (var module in assembly.Modules)
-                        {
-                            AnalyseNamespace(cx, module.GlobalNamespace);
-                        }
-
-                        Entities.Attribute.ExtractAttributes(cx, assembly, Entities.Assembly.Create(cx, assembly.GetSymbolLocation()));
-
-                        cx.PopulateAll();
-                    }
-                }
-
-                ReportProgress(assemblyPath, trapWriter.TrapFile, stopwatch.Elapsed, skipExtraction ? AnalysisAction.UpToDate : AnalysisAction.Extracted);
-            }
-            catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
-            {
-                Logger.Log(Severity.Error, "  Unhandled exception analyzing {0}: {1}", r.FilePath, ex);
-            }
-        }
-
-        private void DoExtractCIL(PortableExecutableReference r)
-        {
-            var stopwatch = new Stopwatch();
-            stopwatch.Start();
-            CIL.Analyser.ExtractCIL(layout, r.FilePath, Logger, !options.Cache, options.PDB, options.TrapCompression, out var trapFile, out var extracted);
-            stopwatch.Stop();
-            ReportProgress(r.FilePath, trapFile, stopwatch.Elapsed, extracted ? AnalysisAction.Extracted : AnalysisAction.UpToDate);
-        }
-
-        private void AnalyseNamespace(Context cx, INamespaceSymbol ns)
-        {
-            foreach (var memberNamespace in ns.GetNamespaceMembers())
-            {
-                AnalyseNamespace(cx, memberNamespace);
-            }
-
-            foreach (var memberType in ns.GetTypeMembers())
-            {
-                Entities.Type.Create(cx, memberType).ExtractRecursive();
-            }
-        }
-
-        /// <summary>
-        ///     Enqueue all reference analysis tasks.
-        /// </summary>
-        public void AnalyseReferences()
-        {
-            foreach (var r in compilation.References.OfType<PortableExecutableReference>())
-            {
-                AnalyseReferenceAssembly(r);
-            }
-        }
-
-        // The bulk of the extraction work, potentially executed in parallel.
-        private readonly List<Action> extractionTasks = new List<Action>();
-
-        private void ReportProgress(string src, string output, TimeSpan time, AnalysisAction action)
-        {
-            lock (progressMutex)
-                progressMonitor.Analysed(++taskCount, extractionTasks.Count, src, output, time, action);
-        }
-
-        private void DoExtractTree(SyntaxTree tree)
-        {
-            try
-            {
-                var stopwatch = new Stopwatch();
-                stopwatch.Start();
-                var sourcePath = tree.FilePath;
-                var transformedSourcePath = PathTransformer.Transform(sourcePath);
-
-                var projectLayout = layout.LookupProjectOrNull(transformedSourcePath);
-                var excluded = projectLayout == null;
-                var trapPath = excluded ? "" : projectLayout.GetTrapPath(Logger, transformedSourcePath, options.TrapCompression);
-                var upToDate = false;
-
-                if (!excluded)
-                {
-                    // compilation.Clone() is used to allow symbols to be garbage collected.
-                    using var trapWriter = projectLayout.CreateTrapWriter(Logger, transformedSourcePath, options.TrapCompression, discardDuplicates: false);
-
-                    upToDate = options.Fast && FileIsUpToDate(sourcePath, trapWriter.TrapFile);
-
-                    if (!upToDate)
-                    {
-                        var cx = new Context(extractor, compilation.Clone(), trapWriter, new SourceScope(tree), AddAssemblyTrapPrefix);
-                        // Ensure that the file itself is populated in case the source file is totally empty
-                        var root = tree.GetRoot();
-                        Entities.File.Create(cx, root.SyntaxTree.FilePath);
-
-                        var csNode = (CSharpSyntaxNode)root;
-                        csNode.Accept(new CompilationUnitVisitor(cx));
-                        csNode.Accept(new DirectiveVisitor(cx));
-                        cx.PopulateAll();
-                        CommentPopulator.ExtractCommentBlocks(cx, cx.CommentGenerator);
-                        cx.PopulateAll();
-                    }
-                }
-
-                ReportProgress(sourcePath, trapPath, stopwatch.Elapsed, excluded
-                    ? AnalysisAction.Excluded
-                    : upToDate
-                        ? AnalysisAction.UpToDate
-                        : AnalysisAction.Extracted);
-            }
-            catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
-            {
-                extractor.Message(new Message($"Unhandled exception processing syntax tree. {ex.Message}", tree.FilePath, null, ex.StackTrace));
-            }
-        }
-
-        /// <summary>
-        /// Run all extraction tasks.
-        /// </summary>
-        /// <param name="numberOfThreads">The number of threads to use.</param>
-        public void PerformExtraction(int numberOfThreads)
-        {
-            Parallel.Invoke(
-                new ParallelOptions { MaxDegreeOfParallelism = numberOfThreads },
-                extractionTasks.ToArray());
-        }
-
-        public void Dispose()
-        {
-            compilationTrapFile?.Dispose();
-
-            stopWatch.Stop();
-            Logger.Log(Severity.Info, "  Peak working set = {0} MB", Process.GetCurrentProcess().PeakWorkingSet64 / (1024 * 1024));
-
-            if (TotalErrors > 0)
-                Logger.Log(Severity.Info, "EXTRACTION FAILED with {0} error{1} in {2}", TotalErrors, TotalErrors == 1 ? "" : "s", stopWatch.Elapsed);
-            else
-                Logger.Log(Severity.Info, "EXTRACTION SUCCEEDED in {0}", stopWatch.Elapsed);
-
-            Logger.Dispose();
-        }
-
-        /// <summary>
-        /// Number of errors encountered during extraction.
-        /// </summary>
-        public int ExtractorErrors => extractor == null ? 0 : extractor.Errors;
-
-        /// <summary>
-        /// Number of errors encountered by the compiler.
-        /// </summary>
-        public int CompilationErrors { get; set; }
-
-        /// <summary>
-        /// Total number of errors reported.
-        /// </summary>
-        public int TotalErrors => CompilationErrors + ExtractorErrors;
-
-        /// <summary>
-        /// Logs information about the extractor.
-        /// </summary>
-        public void LogExtractorInfo(string extractorVersion)
-        {
-            Logger.Log(Severity.Info, "  Extractor: {0}", Environment.GetCommandLineArgs().First());
-            Logger.Log(Severity.Info, "  Extractor version: {0}", extractorVersion);
-            Logger.Log(Severity.Info, "  Current working directory: {0}", Directory.GetCurrentDirectory());
-        }
-
-        /// <summary>
-        /// Logs information about the extractor, as well as the arguments to Roslyn.
-        /// </summary>
-        /// <param name="roslynArgs">The arguments passed to Roslyn.</param>
-        /// <returns>A Boolean indicating whether the same arguments have been logged previously.</returns>
-        private bool LogRoslynArgs(IEnumerable<string> roslynArgs, string extractorVersion)
-        {
-            LogExtractorInfo(extractorVersion);
-            Logger.Log(Severity.Info, $"  Arguments to Roslyn: {string.Join(' ', roslynArgs)}");
-
-            var tempFile = Extractor.GetCSharpArgsLogPath(Path.GetRandomFileName());
-
-            bool argsWritten;
-            using (var streamWriter = new StreamWriter(new FileStream(tempFile, FileMode.Append, FileAccess.Write)))
-            {
-                streamWriter.WriteLine($"# Arguments to Roslyn: {string.Join(' ', roslynArgs.Where(arg => !arg.StartsWith('@')))}");
-                argsWritten = roslynArgs.WriteCommandLine(streamWriter);
-            }
-
-            var hash = FileUtils.ComputeFileHash(tempFile);
-            var argsFile = Extractor.GetCSharpArgsLogPath(hash);
-
-            if (argsWritten)
-                Logger.Log(Severity.Info, $"  Arguments have been written to {argsFile}");
-
-            if (File.Exists(argsFile))
-            {
-                try
-                {
-                    File.Delete(tempFile);
-                }
-                catch (IOException e)
-                {
-                    Logger.Log(Severity.Warning, $"  Failed to remove {tempFile}: {e.Message}");
-                }
-                return false;
-            }
-
-            try
-            {
-                File.Move(tempFile, argsFile);
-            }
-            catch (IOException e)
-            {
-                Logger.Log(Severity.Warning, $"  Failed to move {tempFile} to {argsFile}: {e.Message}");
-            }
-
-            return true;
-        }
-
-
-        /// <summary>
-        /// Logs detailed information about this invocation,
-        /// in the event that errors were detected.
-        /// </summary>
-        /// <returns>A Boolean indicating whether to proceed with extraction.</returns>
-        public void LogDiagnostics()
-        {
-            foreach (var error in FilteredDiagnostics)
-            {
-                Logger.Log(Severity.Error, "  Compilation error: {0}", error);
-            }
-
-            if (FilteredDiagnostics.Any())
-            {
-                foreach (var reference in compilation.References)
-                {
-                    Logger.Log(Severity.Info, "  Resolved reference {0}", reference.Display);
-                }
-            }
-        }
-    }
-
-    /// <summary>
-    /// What action was performed when extracting a file.
-    /// </summary>
-    public enum AnalysisAction
-    {
-        Extracted,
-        UpToDate,
-        Excluded
-    }
-
-    /// <summary>
-    /// Callback for various extraction events.
-    /// (Used for display of progress).
-    /// </summary>
-    public interface IProgressMonitor
-    {
-        /// <summary>
-        /// Callback that a particular item has been analysed.
-        /// </summary>
-        /// <param name="item">The item number being processed.</param>
-        /// <param name="total">The total number of items to process.</param>
-        /// <param name="source">The name of the item, e.g. a source file.</param>
-        /// <param name="output">The name of the item being output, e.g. a trap file.</param>
-        /// <param name="time">The time to extract the item.</param>
-        /// <param name="action">What action was taken for the file.</param>
-        void Analysed(int item, int total, string source, string output, TimeSpan time, AnalysisAction action);
-
-        /// <summary>
-        /// A "using namespace" directive was seen but the given
-        /// namespace could not be found.
-        /// Only called once for each @namespace.
-        /// </summary>
-        /// <param name="namespace"></param>
-        void MissingNamespace(string @namespace);
-
-        /// <summary>
-        /// An ErrorType was found.
-        /// Called once for each type name.
-        /// </summary>
-        /// <param name="type">The full/partial name of the type.</param>
-        void MissingType(string type);
-
-        /// <summary>
-        /// Report a summary of missing entities.
-        /// </summary>
-        /// <param name="types">The number of missing types.</param>
-        /// <param name="namespaces">The number of missing using namespace declarations.</param>
-        void MissingSummary(int types, int namespaces);
-    }
-}

csharp/extractor/Semmle.Extraction.CSharp/Comments/CommentProcessor.cs

@@ -26,7 +26,7 @@ namespace Semmle.Extraction.CSharp
 
         private readonly Dictionary<Label, Key> duplicationGuardKeys = new Dictionary<Label, Key>();
 
-        private Key GetDuplicationGuardKey(Label label)
+        private Key? GetDuplicationGuardKey(Label label)
         {
             if (duplicationGuardKeys.TryGetValue(label, out var duplicationGuardKey))
                 return duplicationGuardKey;
@@ -35,7 +35,7 @@ namespace Semmle.Extraction.CSharp
 
         private class LocationComparer : IComparer<Location>
         {
-            public int Compare(Location l1, Location l2) => CommentProcessor.Compare(l1, l2);
+            public int Compare(Location? l1, Location? l2) => CommentProcessor.Compare(l1, l2);
         }
 
         /// <summary>
@@ -44,7 +44,7 @@ namespace Semmle.Extraction.CSharp
         /// <param name="l1">First location</param>
         /// <param name="l2">Second location</param>
         /// <returns>&lt;0 if l1 before l2, &gt;0 if l1 after l2, else 0.</returns>
-        private static int Compare(Location l1, Location l2)
+        private static int Compare(Location? l1, Location? l2)
         {
             if (object.ReferenceEquals(l1, l2))
                 return 0;
@@ -68,7 +68,7 @@ namespace Semmle.Extraction.CSharp
         /// <param name="elementLabel">The label of the element in the trap file.</param>
         /// <param name="duplicationGuardKey">The duplication guard key of the element, if any.</param>
         /// <param name="loc">The location of the element.</param>
-        public void AddElement(Label elementLabel, Key duplicationGuardKey, Location loc)
+        public void AddElement(Label elementLabel, Key? duplicationGuardKey, Location? loc)
         {
             if (loc != null && loc.IsInSource)
                 elements[loc] = elementLabel;
@@ -265,7 +265,7 @@ namespace Semmle.Extraction.CSharp
             CommentBindingCallback cb
             )
         {
-            Comments.CommentBlock block = null;
+            Comments.CommentBlock? block = null;
 
             // Iterate comments until the commentEnumerator has gone past nextElement
             while (nextElement == null || Compare(commentEnumerator.Current.Value.Location, nextElement.Value.Key) < 0)
@@ -350,5 +350,5 @@ namespace Semmle.Extraction.CSharp
     /// <param name="duplicationGuardKey">The duplication guard key of the element, if any</param>
     /// <param name="commentBlock">The comment block associated with the element</param>
     /// <param name="binding">The relationship between the commentblock and the element</param>
-    internal delegate void CommentBindingCallback(Label elementLabel, Key duplicationGuardKey, Comments.CommentBlock commentBlock, CommentBinding binding);
+    internal delegate void CommentBindingCallback(Label elementLabel, Key? duplicationGuardKey, Comments.CommentBlock commentBlock, CommentBinding binding);
 }

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

@@ -13,7 +13,7 @@ namespace Semmle.Extraction.CSharp.Entities
         /// Gets the property symbol associated accessor `symbol`, or `null`
         /// if there is no associated symbol.
         /// </summary>
-        public static IPropertySymbol GetPropertySymbol(IMethodSymbol symbol)
+        public static IPropertySymbol? GetPropertySymbol(IMethodSymbol symbol)
         {
             // Usually, the property/indexer can be fetched from the associated symbol
             if (symbol.AssociatedSymbol is IPropertySymbol prop)
@@ -29,7 +29,7 @@ namespace Semmle.Extraction.CSharp.Entities
         /// <summary>
         /// Gets the property symbol associated with this accessor.
         /// </summary>
-        private IPropertySymbol PropertySymbol => GetPropertySymbol(Symbol);
+        private IPropertySymbol? PropertySymbol => GetPropertySymbol(Symbol);
 
         public new Accessor OriginalDefinition => Create(Context, Symbol.OriginalDefinition);
 
@@ -37,7 +37,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             PopulateMethod(trapFile);
             PopulateModifiers(trapFile);
-            ContainingType.PopulateGenerics();
+            ContainingType!.PopulateGenerics();
 
             var prop = PropertySymbol;
             if (prop == null)
@@ -52,12 +52,12 @@ namespace Semmle.Extraction.CSharp.Entities
             if (SymbolEqualityComparer.Default.Equals(Symbol, prop.GetMethod))
             {
                 kind = 1;
-                unboundAccessor = Create(Context, prop.OriginalDefinition.GetMethod);
+                unboundAccessor = Create(Context, prop.OriginalDefinition.GetMethod!);
             }
             else if (SymbolEqualityComparer.Default.Equals(Symbol, prop.SetMethod))
             {
                 kind = 2;
-                unboundAccessor = Create(Context, prop.OriginalDefinition.SetMethod);
+                unboundAccessor = Create(Context, prop.OriginalDefinition.SetMethod!);
             }
             else
             {

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

@@ -6,19 +6,18 @@ namespace Semmle.Extraction.CSharp.Entities
 {
     internal class Assembly : Extraction.Entities.Location
     {
-        // todo: this can be changed to an override after the .NET 5 upgrade
-        private new Context Context => (Context)base.Context;
+        public override Context Context => (Context)base.Context;
 
         private readonly string assemblyPath;
         private readonly IAssemblySymbol assembly;
 
-        private Assembly(Context cx, Microsoft.CodeAnalysis.Location init)
+        private Assembly(Context cx, Microsoft.CodeAnalysis.Location? init)
             : base(cx, init)
         {
             if (init == null)
             {
                 // This is the output assembly
-                assemblyPath = cx.Extractor.OutputPath;
+                assemblyPath = ((TracingExtractor)cx.Extractor).OutputPath;
                 assembly = cx.Compilation.Assembly;
             }
             else
@@ -44,7 +43,7 @@ namespace Semmle.Extraction.CSharp.Entities
         public override int GetHashCode() =>
             Symbol == null ? 91187354 : Symbol.GetHashCode();
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (obj is Assembly other && other.GetType() == typeof(Assembly))
                 return Equals(Symbol, other.Symbol);
@@ -54,18 +53,18 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public static Extraction.Entities.Location Create(Context cx, Microsoft.CodeAnalysis.Location loc) => AssemblyConstructorFactory.Instance.CreateEntity(cx, loc, loc);
 
-        private class AssemblyConstructorFactory : CachedEntityFactory<Microsoft.CodeAnalysis.Location, Assembly>
+        private class AssemblyConstructorFactory : CachedEntityFactory<Microsoft.CodeAnalysis.Location?, Assembly>
         {
             public static AssemblyConstructorFactory Instance { get; } = new AssemblyConstructorFactory();
 
-            public override Assembly Create(Context cx, Microsoft.CodeAnalysis.Location init) => new Assembly(cx, init);
+            public override Assembly Create(Context cx, Microsoft.CodeAnalysis.Location? init) => new Assembly(cx, init);
         }
 
         private static readonly object outputAssemblyCacheKey = new object();
 
         public static Assembly CreateOutputAssembly(Context cx)
         {
-            if (cx.Extractor.OutputPath == null)
+            if (cx.Extractor.Standalone)
                 throw new InternalError("Attempting to create the output assembly in standalone extraction mode");
             return AssemblyConstructorFactory.Instance.CreateEntity(cx, outputAssemblyCacheKey, null);
         }

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

@@ -10,7 +10,7 @@ namespace Semmle.Extraction.CSharp.Entities
     {
         bool IExpressionParentEntity.IsTopLevelParent => true;
 
-        private readonly AttributeSyntax attributeSyntax;
+        private readonly AttributeSyntax? attributeSyntax;
         private readonly IEntity entity;
 
         private Attribute(Context cx, AttributeData attributeData, IEntity entity)
@@ -53,7 +53,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
             if (attributeSyntax is object)
             {
-                if (Context.Extractor.OutputPath != null)
+                if (!Context.Extractor.Standalone)
                 {
                     trapFile.attribute_location(this, Assembly.CreateOutputAssembly(Context));
                 }
@@ -93,7 +93,7 @@ namespace Semmle.Extraction.CSharp.Entities
             {
                 var expr = CreateExpressionFromArgument(
                     namedArgument.Value,
-                    attributeSyntax?.ArgumentList.Arguments.Single(a => a.NameEquals?.Name?.Identifier.Text == namedArgument.Key).Expression,
+                    attributeSyntax?.ArgumentList?.Arguments.Single(a => a.NameEquals?.Name?.Identifier.Text == namedArgument.Key).Expression,
                     this,
                     childIndex++);
 
@@ -104,7 +104,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        private Expression CreateExpressionFromArgument(TypedConstant constant, ExpressionSyntax syntax, IExpressionParentEntity parent,
+        private Expression? CreateExpressionFromArgument(TypedConstant constant, ExpressionSyntax? syntax, IExpressionParentEntity parent,
             int childIndex)
         {
             return syntax is null
@@ -114,11 +114,14 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override TrapStackBehaviour TrapStackBehaviour => TrapStackBehaviour.OptionalLabel;
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => attributeSyntax?.Name.GetLocation();
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => attributeSyntax?.Name.GetLocation();
+
+        private Semmle.Extraction.Entities.Location? location;
 
-        private Semmle.Extraction.Entities.Location location;
         private Semmle.Extraction.Entities.Location Location =>
-            location ?? (location = Context.CreateLocation(attributeSyntax is null ? entity.ReportingLocation : attributeSyntax.Name.GetLocation()));
+            location ??= Context.CreateLocation(attributeSyntax is null
+                ? entity.ReportingLocation
+                : attributeSyntax.Name.GetLocation());
 
         public override bool NeedsPopulation => true;
 

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

@@ -1,11 +1,11 @@
 namespace Semmle.Extraction.CSharp.Entities
 {
-    internal abstract class CachedEntity<T> : Extraction.CachedEntity<T>
+    internal abstract class CachedEntity<T> : Extraction.CachedEntity<T> where T : notnull
     {
-        // todo: this can be changed to an override after the .NET 5 upgrade
-        protected new Context Context => (Context)base.Context;
+        public override Context Context => (Context)base.Context;
 
-        protected CachedEntity(Context context, T symbol) : base(context, symbol)
+        protected CachedEntity(Context context, T symbol)
+            : base(context, symbol)
         {
         }
     }

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

@@ -9,17 +9,14 @@ using System.Reflection.Metadata.Ecma335;
 
 namespace Semmle.Extraction.CSharp.Entities
 {
-    internal abstract class CachedSymbol<T> : CachedEntity<T> where T : ISymbol
+    internal abstract class CachedSymbol<T> : CachedEntity<T> where T : class, ISymbol
     {
-        // todo: this can be changed to an override after the .NET 5 upgrade
-        protected new Context Context => (Context)base.Context;
-
         protected CachedSymbol(Context cx, T init)
             : base(cx, init)
         {
         }
 
-        public virtual Type ContainingType => Symbol.ContainingType != null ? Type.Create(Context, Symbol.ContainingType) : null;
+        public virtual Type? ContainingType => Symbol.ContainingType != null ? Type.Create(Context, Symbol.ContainingType) : null;
 
         public void PopulateModifiers(TextWriter trapFile)
         {
@@ -68,12 +65,12 @@ namespace Semmle.Extraction.CSharp.Entities
         /// The location which is stored in the database and is used when highlighing source code.
         /// It's generally short, e.g. a method name.
         /// </summary>
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => Symbol.Locations.FirstOrDefault();
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => Symbol.Locations.FirstOrDefault();
 
         /// <summary>
         /// The full text span of the entity, e.g. for binding comments.
         /// </summary>
-        public virtual Microsoft.CodeAnalysis.Location FullLocation => Symbol.Locations.FirstOrDefault();
+        public virtual Microsoft.CodeAnalysis.Location? FullLocation => Symbol.Locations.FirstOrDefault();
 
         public virtual IEnumerable<Extraction.Entities.Location> Locations
         {
@@ -84,7 +81,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 {
                     // Some built in operators lack locations, so loc is null.
                     yield return Context.CreateLocation(ReportingLocation);
-                    if (Context.Extractor.OutputPath != null && loc.Kind == LocationKind.SourceFile)
+                    if (!Context.Extractor.Standalone && loc.Kind == LocationKind.SourceFile)
                         yield return Assembly.CreateOutputAssembly(Context);
                 }
             }
@@ -102,7 +99,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         protected virtual T BodyDeclaringSymbol => Symbol;
 
-        public BlockSyntax Block
+        public BlockSyntax? Block
         {
             get
             {
@@ -113,7 +110,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        public ExpressionSyntax ExpressionBody
+        public ExpressionSyntax? ExpressionBody
         {
             get
             {
@@ -139,7 +136,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 trapFile.metadata_handle(this, Location, MetadataTokens.GetToken(handle.Value));
         }
 
-        private static System.Reflection.PropertyInfo GetPropertyInfo(object o, string name)
+        private static System.Reflection.PropertyInfo? GetPropertyInfo(object o, string name)
         {
             return o.GetType().GetProperty(name, System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.GetProperty);
         }

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

@@ -1,5 +1,6 @@
 using Semmle.Extraction.Entities;
 using System.IO;
+using System;
 
 namespace Semmle.Extraction.CSharp.Entities
 {
@@ -18,7 +19,7 @@ namespace Semmle.Extraction.CSharp.Entities
         public string Text { get { return Symbol.Item2; } }
         public string RawText { get; private set; }
 
-        private Location location;
+        private Location? location;
 
         public override void Populate(TextWriter trapFile)
         {
@@ -27,7 +28,7 @@ namespace Semmle.Extraction.CSharp.Entities
             trapFile.commentline_location(this, location);
         }
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => location.Symbol;
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => location?.Symbol;
 
         public override bool NeedsPopulation => true;
 

csharp/extractor/Semmle.Extraction.CSharp/Entities/Compilations/Compilation.cs

@@ -25,9 +25,11 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
+#nullable disable warnings
         private Compilation(Context cx) : base(cx, null)
         {
         }
+#nullable restore warnings
 
         public override void Populate(TextWriter trapFile)
         {
@@ -54,7 +56,8 @@ namespace Semmle.Extraction.CSharp.Entities
             index = 0;
             foreach (var file in Context.Compilation.References
                 .OfType<PortableExecutableReference>()
-                .Select(r => File.Create(Context, r.FilePath)))
+                .Where(r => r.FilePath is object)
+                .Select(r => File.Create(Context, r.FilePath!)))
             {
                 trapFile.compilation_referencing_files(this, index++, file);
             }
@@ -90,11 +93,11 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override bool NeedsPopulation => Context.IsAssemblyScope;
 
-        private class CompilationFactory : CachedEntityFactory<object, Compilation>
+        private class CompilationFactory : CachedEntityFactory<object?, Compilation>
         {
             public static CompilationFactory Instance { get; } = new CompilationFactory();
 
-            public override Compilation Create(Context cx, object init) => new Compilation(cx);
+            public override Compilation Create(Context cx, object? init) => new Compilation(cx);
         }
 
         private static readonly object compilationCacheKey = new object();

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

@@ -5,6 +5,7 @@ using System.Linq;
 using Microsoft.CodeAnalysis.CSharp;
 using Semmle.Extraction.Entities;
 using System.IO;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Semmle.Extraction.CSharp.Entities
 {
@@ -17,7 +18,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             PopulateMethod(trapFile);
             PopulateModifiers(trapFile);
-            ContainingType.PopulateGenerics();
+            ContainingType!.PopulateGenerics();
 
             trapFile.constructors(this, Symbol.ContainingType.Name, ContainingType, (Constructor)OriginalDefinition);
             trapFile.constructor_location(this, Location);
@@ -48,7 +49,7 @@ namespace Semmle.Extraction.CSharp.Entities
             switch (initializer.Kind())
             {
                 case SyntaxKind.BaseConstructorInitializer:
-                    initializerType = Symbol.ContainingType.BaseType;
+                    initializerType = Symbol.ContainingType.BaseType!;
                     break;
                 case SyntaxKind.ThisConstructorInitializer:
                     initializerType = Symbol.ContainingType;
@@ -69,8 +70,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
             var init = new Expression(initInfo);
 
-            var target = Constructor.Create(Context, (IMethodSymbol)symbolInfo.Symbol);
-
+            var target = Constructor.Create(Context, (IMethodSymbol?)symbolInfo.Symbol);
             if (target == null)
             {
                 Context.ModelError(Symbol, "Unable to resolve call");
@@ -86,7 +86,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        private ConstructorDeclarationSyntax Syntax
+        private ConstructorDeclarationSyntax? Syntax
         {
             get
             {
@@ -97,7 +97,8 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        public static new Constructor Create(Context cx, IMethodSymbol constructor)
+        [return: NotNullIfNotNull("constructor")]
+        public static new Constructor? Create(Context cx, IMethodSymbol? constructor)
         {
             if (constructor == null)
                 return null;
@@ -116,17 +117,17 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             if (Symbol.IsStatic)
                 trapFile.Write("static");
-            trapFile.WriteSubId(ContainingType);
+            trapFile.WriteSubId(ContainingType!);
             AddParametersToId(Context, trapFile, Symbol);
             trapFile.Write(";constructor");
         }
 
-        private ConstructorDeclarationSyntax GetSyntax() =>
+        private ConstructorDeclarationSyntax? GetSyntax() =>
             Symbol.DeclaringSyntaxReferences.Select(r => r.GetSyntax()).OfType<ConstructorDeclarationSyntax>().FirstOrDefault();
 
-        public override Microsoft.CodeAnalysis.Location FullLocation => ReportingLocation;
+        public override Microsoft.CodeAnalysis.Location? FullLocation => ReportingLocation;
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation
         {
             get
             {
@@ -138,7 +139,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
                 if (Symbol.IsImplicitlyDeclared)
                 {
-                    return ContainingType.ReportingLocation;
+                    return ContainingType!.ReportingLocation;
                 }
 
                 return Symbol.ContainingType.Locations.FirstOrDefault();

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

@@ -13,7 +13,7 @@ namespace Semmle.Extraction.CSharp.Entities
         public static new Conversion Create(Context cx, IMethodSymbol symbol) =>
             ConversionFactory.Instance.CreateEntityFromSymbol(cx, symbol);
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation
         {
             get
             {

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

@@ -12,7 +12,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             PopulateMethod(trapFile);
             PopulateModifiers(trapFile);
-            ContainingType.PopulateGenerics();
+            ContainingType!.PopulateGenerics();
 
             trapFile.destructors(this, string.Format("~{0}", Symbol.ContainingType.Name), ContainingType, OriginalDefinition(Context, this, Symbol));
             trapFile.destructor_location(this, Location);

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

@@ -12,7 +12,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override void WriteId(TextWriter trapFile)
         {
-            trapFile.WriteSubId(ContainingType);
+            trapFile.WriteSubId(ContainingType!);
             trapFile.Write('.');
             Method.AddExplicitInterfaceQualifierToId(Context, trapFile, Symbol.ExplicitInterfaceImplementations);
             trapFile.Write(Symbol.Name);
@@ -24,7 +24,7 @@ namespace Semmle.Extraction.CSharp.Entities
             PopulateNullability(trapFile, Symbol.GetAnnotatedType());
 
             var type = Type.Create(Context, Symbol.Type);
-            trapFile.events(this, Symbol.GetName(), ContainingType, type.TypeRef, Create(Context, Symbol.OriginalDefinition));
+            trapFile.events(this, Symbol.GetName(), ContainingType!, type.TypeRef, Create(Context, Symbol.OriginalDefinition));
 
             var adder = Symbol.AddMethod;
             var remover = Symbol.RemoveMethod;
@@ -47,7 +47,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 trapFile.explicitly_implements(this, explicitInterface.TypeRef);
 
                 foreach (var syntax in declSyntaxReferences.OfType<EventDeclarationSyntax>())
-                    TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier.Name, this, explicitInterface);
+                    TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
             foreach (var l in Locations)

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

@@ -11,12 +11,12 @@ namespace Semmle.Extraction.CSharp.Entities
         /// <summary>
         /// Gets the event symbol associated with this accessor.
         /// </summary>
-        private IEventSymbol EventSymbol => Symbol.AssociatedSymbol as IEventSymbol;
+        private IEventSymbol? EventSymbol => Symbol.AssociatedSymbol as IEventSymbol;
 
         public override void Populate(TextWriter trapFile)
         {
             PopulateMethod(trapFile);
-            ContainingType.PopulateGenerics();
+            ContainingType!.PopulateGenerics();
 
             var @event = EventSymbol;
             if (@event == null)
@@ -31,12 +31,12 @@ namespace Semmle.Extraction.CSharp.Entities
             if (SymbolEqualityComparer.Default.Equals(Symbol, @event.AddMethod))
             {
                 kind = 1;
-                unboundAccessor = Create(Context, @event.OriginalDefinition.AddMethod);
+                unboundAccessor = Create(Context, @event.OriginalDefinition.AddMethod!);
             }
             else if (SymbolEqualityComparer.Default.Equals(Symbol, @event.RemoveMethod))
             {
                 kind = 2;
-                unboundAccessor = Create(Context, @event.OriginalDefinition.RemoveMethod);
+                unboundAccessor = Create(Context, @event.OriginalDefinition.RemoveMethod!);
             }
             else
             {

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

@@ -57,7 +57,7 @@ namespace Semmle.Extraction.CSharp.Entities
             type.PopulateGenerics();
         }
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => Location.Symbol;
+        public override Location? ReportingLocation => Location.Symbol;
 
         bool IExpressionParentEntity.IsTopLevelParent => false;
 
@@ -66,7 +66,7 @@ namespace Semmle.Extraction.CSharp.Entities
         /// </summary>
         /// <param name="obj">The value.</param>
         /// <returns>The string representation.</returns>
-        public static string ValueAsString(object value)
+        public static string ValueAsString(object? value)
         {
             return value == null
                 ? "null"
@@ -74,7 +74,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     ? b
                         ? "true"
                         : "false"
-                    : value.ToString();
+                    : value.ToString()!;
         }
 
         /// <summary>
@@ -118,10 +118,11 @@ namespace Semmle.Extraction.CSharp.Entities
         /// <summary>
         /// Creates a generated expression from a typed constant.
         /// </summary>
-        public static Expression CreateGenerated(Context cx, TypedConstant constant, IExpressionParentEntity parent,
-            int childIndex, Semmle.Extraction.Entities.Location location)
+        public static Expression? CreateGenerated(Context cx, TypedConstant constant, IExpressionParentEntity parent,
+            int childIndex, Extraction.Entities.Location location)
         {
-            if (constant.IsNull)
+            if (constant.IsNull ||
+                constant.Type is null)
             {
                 return Literal.CreateGeneratedNullLiteral(cx, parent, childIndex, location);
             }
@@ -132,11 +133,11 @@ namespace Semmle.Extraction.CSharp.Entities
                     return Literal.CreateGenerated(cx, parent, childIndex, constant.Type, constant.Value, location);
                 case TypedConstantKind.Enum:
                     // Enum value is generated in the following format: (Enum)value
-                    Action<Expression, int> createChild = (parent, index) => Literal.CreateGenerated(cx, parent, index, ((INamedTypeSymbol)constant.Type).EnumUnderlyingType, constant.Value, location);
-                    var cast = Cast.CreateGenerated(cx, parent, childIndex, constant.Type, constant.Value, createChild, location);
+                    Action<Expression, int> createChild = (parent, index) => Literal.CreateGenerated(cx, parent, index, ((INamedTypeSymbol)constant.Type).EnumUnderlyingType!, constant.Value, location);
+                    var cast = Cast.CreateGenerated(cx, parent, childIndex, constant.Type!, constant.Value, createChild, location);
                     return cast;
                 case TypedConstantKind.Type:
-                    var type = ((ITypeSymbol)constant.Value).OriginalDefinition;
+                    var type = ((ITypeSymbol)constant.Value!).OriginalDefinition;
                     return TypeOf.CreateGenerated(cx, parent, childIndex, type, location);
                 case TypedConstantKind.Array:
                     // Single dimensional arrays are in the following format:
@@ -145,6 +146,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     //
                     // itemI is generated recursively.
                     return NormalArrayCreation.CreateGenerated(cx, parent, childIndex, constant.Type, constant.Values, location);
+                case TypedConstantKind.Error:
                 default:
                     cx.ExtractionError("Couldn't extract constant in attribute", constant.ToString(), location);
                     return null;
@@ -242,7 +244,7 @@ namespace Semmle.Extraction.CSharp.Entities
         /// <returns>The qualifier of the conditional access.</returns>
         protected static ExpressionSyntax FindConditionalQualifier(ExpressionSyntax node)
         {
-            for (SyntaxNode n = node; n != null; n = n.Parent)
+            for (SyntaxNode? n = node; n != null; n = n.Parent)
             {
                 if (n.Parent is ConditionalAccessExpressionSyntax conditionalAccess &&
                     conditionalAccess.WhenNotNull == n)

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

@@ -15,10 +15,10 @@ namespace Semmle.Extraction.CSharp.Entities
         public IExpressionParentEntity Parent { get; }
         public int Child { get; }
         public bool IsCompilerGenerated { get; }
-        public string ExprValue { get; }
+        public string? ExprValue { get; }
 
         public ExpressionInfo(Context cx, AnnotatedTypeSymbol? type, Extraction.Entities.Location location, ExprKind kind,
-            IExpressionParentEntity parent, int child, bool isCompilerGenerated, string value)
+            IExpressionParentEntity parent, int child, bool isCompilerGenerated, string? value)
         {
             Context = cx;
             Type = type;

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

@@ -74,7 +74,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        private Microsoft.CodeAnalysis.Location location;
+        private Microsoft.CodeAnalysis.Location? location;
 
         public Microsoft.CodeAnalysis.Location CodeAnalysisLocation
         {
@@ -92,7 +92,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public SemanticModel Model => Context.GetModel(Node);
 
-        public string ExprValue
+        public string? ExprValue
         {
             get
             {
@@ -111,7 +111,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        private Extraction.Entities.Location cachedLocation;
+        private Extraction.Entities.Location? cachedLocation;
 
         public Extraction.Entities.Location Location
         {

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

@@ -21,9 +21,9 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
     {
         protected ExplicitArrayCreation(ExpressionNodeInfo info) : base(info.SetKind(ExprKind.ARRAY_CREATION)) { }
 
-        protected abstract ArrayTypeSyntax TypeSyntax { get; }
+        protected abstract ArrayTypeSyntax? TypeSyntax { get; }
 
-        public abstract InitializerExpressionSyntax Initializer { get; }
+        public abstract InitializerExpressionSyntax? Initializer { get; }
 
         protected override void PopulateExpression(TextWriter trapFile)
         {
@@ -32,6 +32,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             if (TypeSyntax is null)
             {
                 Context.ModelError(Syntax, "Array has unexpected type syntax");
+                return;
             }
 
             var firstLevelSizes = TypeSyntax.RankSpecifiers.First()?.Sizes ?? SyntaxFactory.SeparatedList<ExpressionSyntax>();
@@ -60,7 +61,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             TypeMention.Create(Context, TypeSyntax, this, Type);
         }
 
-        private void SetArraySizes(InitializerExpressionSyntax initializer, int rank)
+        private void SetArraySizes(InitializerExpressionSyntax? initializer, int rank)
         {
             for (var level = 0; level < rank; level++)
             {
@@ -82,7 +83,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 
         protected override ArrayTypeSyntax TypeSyntax => Syntax.Type;
 
-        public override InitializerExpressionSyntax Initializer => Syntax.Initializer;
+        public override InitializerExpressionSyntax? Initializer => Syntax.Initializer;
 
         public static Expression Create(ExpressionNodeInfo info) => new NormalArrayCreation(info).TryPopulate();
 
@@ -122,9 +123,9 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
     {
         private StackAllocArrayCreation(ExpressionNodeInfo info) : base(info) { }
 
-        protected override ArrayTypeSyntax TypeSyntax => Syntax.Type as ArrayTypeSyntax;
+        protected override ArrayTypeSyntax? TypeSyntax => Syntax.Type as ArrayTypeSyntax;
 
-        public override InitializerExpressionSyntax Initializer => Syntax.Initializer;
+        public override InitializerExpressionSyntax? Initializer => Syntax.Initializer;
 
         protected override void PopulateExpression(TextWriter trapFile)
         {

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

@@ -32,7 +32,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 
         public override Microsoft.CodeAnalysis.Location ReportingLocation => Syntax.GetLocation();
 
-        public static Expression CreateGenerated(Context cx, IExpressionParentEntity parent, int childIndex, Microsoft.CodeAnalysis.ITypeSymbol type, object value, Action<Expression, int> createChild, Extraction.Entities.Location location)
+        public static Expression CreateGenerated(Context cx, IExpressionParentEntity parent, int childIndex, Microsoft.CodeAnalysis.ITypeSymbol type, object? value, Action<Expression, int> createChild, Extraction.Entities.Location location)
         {
             var info = new ExpressionInfo(
                 cx,

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

@@ -42,7 +42,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             }
         }
 
-        public sealed override Microsoft.CodeAnalysis.Location ReportingLocation => base.ReportingLocation;
+        public sealed override Microsoft.CodeAnalysis.Location? ReportingLocation => base.ReportingLocation;
 
         private static ExprKind GetKind(Context cx, ExpressionSyntax qualifier)
         {

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

@@ -29,7 +29,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             }
 
             var child = -1;
-            string memberName = null;
+            string? memberName = null;
             var target = TargetSymbol;
             switch (Syntax.Expression)
             {
@@ -54,11 +54,15 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
                     if (target != null && !target.IsStatic)
                     {
                         // Implicit `this` qualifier; add explicitly
-
-                        if (Context.GetModel(Syntax).GetEnclosingSymbol(Location.Symbol.SourceSpan.Start) is IMethodSymbol callingMethod)
+                        if (Location.Symbol is object &&
+                            Context.GetModel(Syntax).GetEnclosingSymbol(Location.Symbol.SourceSpan.Start) is IMethodSymbol callingMethod)
+                        {
                             This.CreateImplicit(Context, callingMethod.ContainingType, Location, this, child++);
+                        }
                         else
+                        {
                             Context.ModelError(Syntax, "Couldn't determine implicit this type");
+                        }
                     }
                     else
                     {
@@ -105,7 +109,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 
         public SymbolInfo SymbolInfo => info.SymbolInfo;
 
-        public IMethodSymbol TargetSymbol
+        public IMethodSymbol? TargetSymbol
         {
             get
             {
@@ -144,7 +148,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             return IsDelegateLikeCall(info, IsDelegateInvoke);
         }
 
-        private static bool IsDelegateLikeCall(ExpressionNodeInfo info, Func<ISymbol, bool> check)
+        private static bool IsDelegateLikeCall(ExpressionNodeInfo info, Func<ISymbol?, bool> check)
         {
             var si = info.SymbolInfo;
 
@@ -167,13 +171,13 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             return check(si.Symbol);
         }
 
-        private static bool IsFunctionPointer(ISymbol symbol)
+        private static bool IsFunctionPointer(ISymbol? symbol)
         {
             return symbol != null &&
                 symbol.Kind == SymbolKind.FunctionPointerType;
         }
 
-        private static bool IsDelegateInvoke(ISymbol symbol)
+        private static bool IsDelegateInvoke(ISymbol? symbol)
         {
             return symbol != null &&
                 symbol.Kind == SymbolKind.Method &&

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

@@ -17,7 +17,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 
         private void VisitParameter(ParameterSyntax p)
         {
-            var symbol = Context.GetModel(p).GetDeclaredSymbol(p);
+            var symbol = Context.GetModel(p).GetDeclaredSymbol(p)!;
             Parameter.Create(Context, symbol, this);
         }
 

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

@@ -35,7 +35,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             return GetExprKind(type, info.Node, info.Context);
         }
 
-        private static ExprKind GetExprKind(ITypeSymbol type, ExpressionSyntax expr, Context context)
+        private static ExprKind GetExprKind(ITypeSymbol? type, ExpressionSyntax? expr, Context context)
         {
             switch (type?.SpecialType)
             {
@@ -83,7 +83,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             }
         }
 
-        public static Expression CreateGenerated(Context cx, IExpressionParentEntity parent, int childIndex, ITypeSymbol type, object value,
+        public static Expression CreateGenerated(Context cx, IExpressionParentEntity parent, int childIndex, ITypeSymbol type, object? value,
             Extraction.Entities.Location location)
         {
             var info = new ExpressionInfo(

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

@@ -6,7 +6,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 {
     internal class MemberAccess : Expression
     {
-        private MemberAccess(ExpressionNodeInfo info, ExpressionSyntax qualifier, ISymbol target) : base(info)
+        private MemberAccess(ExpressionNodeInfo info, ExpressionSyntax qualifier, ISymbol? target) : base(info)
         {
             var trapFile = info.Context.TrapWriter.Writer;
             Qualifier = Create(Context, qualifier, this, -1);

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

@@ -23,7 +23,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             if (target == null && symbolInfo.CandidateReason == CandidateReason.OverloadResolutionFailure)
             {
                 // The expression is probably a cast
-                target = info.Context.GetSymbolInfo((CSharpSyntaxNode)info.Node.Parent).Symbol;
+                target = info.Context.GetSymbolInfo((CSharpSyntaxNode)info.Node.Parent!).Symbol;
             }
 
             if (target == null && (symbolInfo.CandidateReason == CandidateReason.Ambiguous || symbolInfo.CandidateReason == CandidateReason.MemberGroup))

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/ObjectCreation/AnonymousObjectCreation.cs

@@ -18,22 +18,25 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
         protected override void PopulateExpression(TextWriter trapFile)
         {
             var target = Context.GetSymbolInfo(Syntax);
-            var method = (IMethodSymbol)target.Symbol;
-
+            var method = (IMethodSymbol?)target.Symbol;
             if (method != null)
             {
                 trapFile.expr_call(this, Method.Create(Context, method));
             }
+
             var child = 0;
 
-            var objectInitializer = Syntax.Initializers.Any() ?
-                new Expression(new ExpressionInfo(Context, Type, Location, ExprKind.OBJECT_INIT, this, -1, false, null)) :
-                null;
+            if (!Syntax.Initializers.Any())
+            {
+                return;
+            }
+
+            var objectInitializer = new Expression(new ExpressionInfo(Context, Type, Location, ExprKind.OBJECT_INIT, this, -1, false, null));
 
             foreach (var init in Syntax.Initializers)
             {
                 // Create an "assignment"
-                var property = Context.GetModel(init).GetDeclaredSymbol(init);
+                var property = Context.GetModel(init).GetDeclaredSymbol(init)!;
                 var propEntity = Property.Create(Context, property);
                 var type = property.GetAnnotatedType();
                 var loc = Context.CreateLocation(init.GetLocation());

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Patterns/PropertyPattern.cs

@@ -14,6 +14,11 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             foreach (var sub in pp.Subpatterns)
             {
                 var p = Expressions.Pattern.Create(cx, sub.Pattern, this, child++);
+                if (sub.NameColon is null)
+                {
+                    Context.ModelError(sub, "Expected to find 'Name:' in pattern.");
+                    continue;
+                }
                 trapFile.exprorstmt_name(p, sub.NameColon.Name.ToString());
             }
         }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Patterns/RelationalPattern.cs

@@ -22,7 +22,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
                 SyntaxKind.GreaterThanEqualsToken => ExprKind.GE_PATTERN,
                 SyntaxKind.LessThanToken => ExprKind.LT_PATTERN,
                 SyntaxKind.GreaterThanToken => ExprKind.GT_PATTERN,
-                _ => throw new InternalError(operatorToken.Parent, $"Relation pattern with operator token '{operatorToken.Kind()}' is not supported."),
+                _ => throw new InternalError(operatorToken.Parent!, $"Relation pattern with operator token '{operatorToken.Kind()}' is not supported."),
             };
         }
     }

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

@@ -21,7 +21,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
         /// </remarks>
         private class QueryCall : Expression
         {
-            public QueryCall(Context cx, IMethodSymbol method, SyntaxNode clause, IExpressionParentEntity parent, int child)
+            public QueryCall(Context cx, IMethodSymbol? method, SyntaxNode clause, IExpressionParentEntity parent, int child)
                 : base(new ExpressionInfo(cx, method?.GetAnnotatedReturnType(),
                         cx.CreateLocation(clause.GetLocation()),
                         ExprKind.METHOD_INVOCATION, parent, child, false, null))
@@ -36,11 +36,11 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
         /// </summary>
         private abstract class Clause
         {
-            protected readonly IMethodSymbol method;
+            protected readonly IMethodSymbol? method;
             protected readonly List<ExpressionSyntax> arguments = new List<ExpressionSyntax>();
             protected readonly SyntaxNode node;
 
-            protected Clause(IMethodSymbol method, SyntaxNode node)
+            protected Clause(IMethodSymbol? method, SyntaxNode node)
             {
                 this.method = method;
                 this.node = node;
@@ -48,10 +48,10 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 
             public ExpressionSyntax Expr => arguments.First();
 
-            public CallClause WithCallClause(IMethodSymbol newMethod, SyntaxNode newNode) =>
+            public CallClause WithCallClause(IMethodSymbol? newMethod, SyntaxNode newNode) =>
                 new CallClause(this, newMethod, newNode);
 
-            public LetClause WithLetClause(IMethodSymbol newMethod, SyntaxNode newNode, ISymbol newDeclaration, SyntaxToken newName) =>
+            public LetClause WithLetClause(IMethodSymbol? newMethod, SyntaxNode newNode, ISymbol newDeclaration, SyntaxToken newName) =>
                 new LetClause(this, newMethod, newNode, newDeclaration, newName);
 
             public Clause AddArgument(ExpressionSyntax arg)
@@ -66,7 +66,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
                 var type = cx.GetType(Expr);
 
                 AnnotatedTypeSymbol? declType;
-                TypeSyntax declTypeSyntax = null;
+                TypeSyntax? declTypeSyntax = null;
                 if (getElement)
                 {
                     if (node is FromClauseSyntax from && from.Type != null)
@@ -126,7 +126,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
                     .FirstOrDefault();
             }
 
-            private static AnnotatedTypeSymbol? GetElementType(Context cx, ITypeSymbol symbol) =>
+            private static AnnotatedTypeSymbol? GetElementType(Context cx, ITypeSymbol? symbol) =>
                 symbol switch
                 {
                     IArrayTypeSymbol a => a.GetAnnotatedElementType(),
@@ -150,7 +150,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             private readonly ISymbol declaration;
             private readonly SyntaxToken name;
 
-            public RangeClause(IMethodSymbol method, SyntaxNode node, ISymbol declaration, SyntaxToken name) : base(method, node)
+            public RangeClause(IMethodSymbol? method, SyntaxNode node, ISymbol declaration, SyntaxToken name) : base(method, node)
             {
                 this.declaration = declaration;
                 this.name = name;
@@ -165,9 +165,9 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             private readonly Clause operand;
             private readonly ISymbol declaration;
             private readonly SyntaxToken name;
-            private ISymbol intoDeclaration;
+            private ISymbol? intoDeclaration;
 
-            public LetClause(Clause operand, IMethodSymbol method, SyntaxNode node, ISymbol declaration, SyntaxToken name) : base(method, node)
+            public LetClause(Clause operand, IMethodSymbol? method, SyntaxNode node, ISymbol declaration, SyntaxToken name) : base(method, node)
             {
                 this.operand = operand;
                 this.declaration = declaration;
@@ -204,7 +204,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
         {
             private readonly Clause operand;
 
-            public CallClause(Clause operand, IMethodSymbol method, SyntaxNode node) : base(method, node)
+            public CallClause(Clause operand, IMethodSymbol? method, SyntaxNode node) : base(method, node)
             {
                 this.operand = operand;
             }
@@ -230,7 +230,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             var info = cx.GetModel(node).GetQueryClauseInfo(node.FromClause);
             var method = info.OperationInfo.Symbol as IMethodSymbol;
 
-            var clauseExpr = new RangeClause(method, node.FromClause, cx.GetModel(node).GetDeclaredSymbol(node.FromClause), node.FromClause.Identifier).AddArgument(node.FromClause.Expression);
+            var clauseExpr = new RangeClause(method, node.FromClause, cx.GetModel(node).GetDeclaredSymbol(node.FromClause)!, node.FromClause.Identifier).AddArgument(node.FromClause.Expression);
 
             foreach (var qc in node.Body.Clauses)
             {
@@ -259,25 +259,25 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
                     case SyntaxKind.FromClause:
                         var fromClause = (FromClauseSyntax)qc;
                         clauseExpr = clauseExpr.
-                            WithLetClause(method, fromClause, cx.GetModel(node).GetDeclaredSymbol(fromClause), fromClause.Identifier).
+                            WithLetClause(method, fromClause, cx.GetModel(node).GetDeclaredSymbol(fromClause)!, fromClause.Identifier).
                             AddArgument(fromClause.Expression);
                         break;
                     case SyntaxKind.LetClause:
                         var letClause = (LetClauseSyntax)qc;
-                        clauseExpr = clauseExpr.WithLetClause(method, letClause, cx.GetModel(node).GetDeclaredSymbol(letClause), letClause.Identifier).
+                        clauseExpr = clauseExpr.WithLetClause(method, letClause, cx.GetModel(node).GetDeclaredSymbol(letClause)!, letClause.Identifier).
                             AddArgument(letClause.Expression);
                         break;
                     case SyntaxKind.JoinClause:
                         var joinClause = (JoinClauseSyntax)qc;
 
-                        clauseExpr = clauseExpr.WithLetClause(method, joinClause, cx.GetModel(node).GetDeclaredSymbol(joinClause), joinClause.Identifier).
+                        clauseExpr = clauseExpr.WithLetClause(method, joinClause, cx.GetModel(node).GetDeclaredSymbol(joinClause)!, joinClause.Identifier).
                             AddArgument(joinClause.InExpression).
                             AddArgument(joinClause.LeftExpression).
                             AddArgument(joinClause.RightExpression);
 
                         if (joinClause.Into != null)
                         {
-                            var into = cx.GetModel(node).GetDeclaredSymbol(joinClause.Into);
+                            var into = cx.GetModel(node).GetDeclaredSymbol(joinClause.Into)!;
                             ((LetClause)clauseExpr).WithInto(into);
                         }
 

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

@@ -13,11 +13,9 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 
         public static Expression Create(ExpressionNodeInfo info) => new Switch(info).TryPopulate();
 
-        public Expression SwitchedExpr { get; private set; }
-
         protected override void PopulateExpression(TextWriter trapFile)
         {
-            SwitchedExpr = Expression.Create(Context, Syntax.GoverningExpression, this, -1);
+            Expression.Create(Context, Syntax.GoverningExpression, this, -1);
             for (var i = 0; i < Syntax.Arms.Count; i++)
             {
                 new SwitchCase(Context, Syntax.Arms[i], this, i);

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

@@ -15,7 +15,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             {
                 case SyntaxKind.SimpleMemberAccessExpression:
                     var maes = (MemberAccessExpressionSyntax)Syntax;
-                    if (Type?.Symbol.ContainingType is null)
+                    if (Type?.Symbol?.ContainingType is null)
                     {
                         // namespace qualifier
                         TypeMention.Create(Context, maes.Name, this, Type, Syntax.GetLocation());

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

@@ -11,7 +11,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
     {
         private VariableDeclaration(IExpressionInfo info) : base(info) { }
 
-        public static VariableDeclaration Create(Context cx, ISymbol symbol, AnnotatedTypeSymbol? type, TypeSyntax optionalSyntax, Extraction.Entities.Location exprLocation, bool isVar, IExpressionParentEntity parent, int child)
+        public static VariableDeclaration Create(Context cx, ISymbol symbol, AnnotatedTypeSymbol? type, TypeSyntax? optionalSyntax, Extraction.Entities.Location exprLocation, bool isVar, IExpressionParentEntity parent, int child)
         {
             var ret = new VariableDeclaration(new ExpressionInfo(cx, type, exprLocation, ExprKind.LOCAL_VAR_DECL, parent, child, false, null));
             cx.Try(null, null, () =>
@@ -102,7 +102,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
         }
 
 
-        private static Expression Create(Context cx, DeclarationExpressionSyntax node, VariableDesignationSyntax designation, IExpressionParentEntity parent, int child)
+        private static Expression Create(Context cx, DeclarationExpressionSyntax node, VariableDesignationSyntax? designation, IExpressionParentEntity parent, int child)
         {
             switch (designation)
             {
@@ -127,12 +127,12 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
 
         public static VariableDeclaration Create(Context cx, CatchDeclarationSyntax d, bool isVar, IExpressionParentEntity parent, int child)
         {
-            var symbol = cx.GetModel(d).GetDeclaredSymbol(d);
+            var symbol = cx.GetModel(d).GetDeclaredSymbol(d)!;
             var type = symbol.GetAnnotatedType();
             var ret = Create(cx, d, type, parent, child);
             cx.Try(d, null, () =>
             {
-                var declSymbol = cx.GetModel(d).GetDeclaredSymbol(d);
+                var declSymbol = cx.GetModel(d).GetDeclaredSymbol(d)!;
                 var l = LocalVariable.Create(cx, declSymbol);
                 l.PopulateManual(ret, isVar);
                 TypeMention.Create(cx, d.Type, ret, type);
@@ -145,7 +145,7 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             var ret = Create(cx, d, type, parent, child);
             cx.Try(d, null, () =>
             {
-                var declSymbol = cx.GetModel(d).GetDeclaredSymbol(d);
+                var declSymbol = cx.GetModel(d).GetDeclaredSymbol(d)!;
                 var localVar = LocalVariable.Create(cx, declSymbol);
                 localVar.PopulateManual(ret, isVar);
 

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

@@ -28,7 +28,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             PopulateMetadataHandle(trapFile);
             PopulateAttributes();
-            ContainingType.PopulateGenerics();
+            ContainingType!.PopulateGenerics();
             PopulateNullability(trapFile, Symbol.GetAnnotatedType());
 
             var unboundFieldKey = Field.Create(Context, Symbol.OriginalDefinition);
@@ -67,7 +67,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 {
                     var loc = Context.CreateLocation(initializer.GetLocation());
 
-                    var fieldAccess = AddInitializerAssignment(trapFile, initializer.Initializer.Value, loc, null, ref child);
+                    var fieldAccess = AddInitializerAssignment(trapFile, initializer.Initializer!.Value, loc, null, ref child);
 
                     if (!Symbol.IsStatic)
                     {
@@ -88,7 +88,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
                 var loc = Context.CreateLocation(initializer.GetLocation());
 
-                AddInitializerAssignment(trapFile, initializer.EqualsValue.Value, loc, constValue, ref child);
+                AddInitializerAssignment(trapFile, initializer.EqualsValue!.Value, loc, constValue, ref child);
             }
 
             if (IsSourceDeclaration)
@@ -105,7 +105,7 @@ namespace Semmle.Extraction.CSharp.Entities
         }
 
         private Expression AddInitializerAssignment(TextWriter trapFile, ExpressionSyntax initializer, Extraction.Entities.Location loc,
-            string constValue, ref int child)
+            string? constValue, ref int child)
         {
             var type = Symbol.GetAnnotatedType();
             var simpleAssignExpr = new Expression(new ExpressionInfo(Context, type, loc, ExprKind.SIMPLE_ASSIGN, this, child++, false, constValue));
@@ -122,7 +122,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             trapFile.WriteSubId(Type);
             trapFile.Write(" ");
-            trapFile.WriteSubId(ContainingType);
+            trapFile.WriteSubId(ContainingType!);
             trapFile.Write('.');
             trapFile.Write(Symbol.Name);
             trapFile.Write(";field");

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

@@ -8,8 +8,7 @@ namespace Semmle.Extraction.CSharp.Entities
 {
     internal class File : Extraction.Entities.File
     {
-        // todo: this can be changed to an override after the .NET 5 upgrade
-        private new Context Context => (Context)base.Context;
+        public override Context Context => (Context)base.Context;
 
         protected File(Context cx, string path)
             : base(cx, path)

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

@@ -2,8 +2,7 @@ namespace Semmle.Extraction.CSharp.Entities
 {
     internal abstract class FreshEntity : Extraction.FreshEntity
     {
-        // todo: this can be changed to an override after the .NET 5 upgrade
-        protected new Context Context => (Context)base.Context;
+        public override Context Context => (Context)base.Context;
 
         protected FreshEntity(Context cx)
             : base(cx)

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

@@ -46,7 +46,7 @@ namespace Semmle.Extraction.CSharp.Entities
         /// If the expression does not have a value, then this
         /// is null.
         /// </summary>
-        string ExprValue { get; }
+        string? ExprValue { get; }
 
         NullableFlowState FlowState { get; }
     }

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

@@ -17,7 +17,7 @@ namespace Semmle.Extraction.CSharp.Entities
             PopulateNullability(trapFile, Symbol.GetAnnotatedType());
 
             var type = Type.Create(Context, Symbol.Type);
-            trapFile.indexers(this, Symbol.GetName(useMetadataName: true), ContainingType, type.TypeRef, OriginalDefinition);
+            trapFile.indexers(this, Symbol.GetName(useMetadataName: true), ContainingType!, type.TypeRef, OriginalDefinition);
             foreach (var l in Locations)
                 trapFile.indexer_location(this, l);
 
@@ -63,7 +63,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 trapFile.explicitly_implements(this, explicitInterface.TypeRef);
 
                 foreach (var syntax in declSyntaxReferences)
-                    TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier.Name, this, explicitInterface);
+                    TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
 
@@ -75,7 +75,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override void WriteId(TextWriter trapFile)
         {
-            trapFile.WriteSubId(ContainingType);
+            trapFile.WriteSubId(ContainingType!);
             trapFile.Write('.');
             trapFile.Write(Symbol.MetadataName);
             trapFile.Write('(');

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

@@ -49,7 +49,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             if (Symbol is ILocalSymbol local && local.HasConstantValue)
             {
-                trapFile.constant_value(this, Expression.ValueAsString(local.ConstantValue));
+                trapFile.constant_value(this, Expression.ValueAsString(local.ConstantValue!));
             }
         }
 

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

@@ -3,6 +3,7 @@ using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Semmle.Extraction.CSharp.Populators;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 
@@ -25,7 +26,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 {
                     // Non-generic reduced extensions must be extracted exactly like the
                     // non-reduced counterparts
-                    parameters = Symbol.ReducedFrom.Parameters;
+                    parameters = Symbol.ReducedFrom!.Parameters;
                 }
                 else
                 {
@@ -82,7 +83,7 @@ namespace Semmle.Extraction.CSharp.Entities
                        if (block != null)
                            Statements.Block.Create(Context, block, this, 0);
                        else
-                           Expression.Create(Context, expr, this, 0);
+                           Expression.Create(Context, expr!, this, 0);
 
                        NumberOfLines(trapFile, BodyDeclaringSymbol, this);
                    });
@@ -95,7 +96,10 @@ namespace Semmle.Extraction.CSharp.Entities
             {
                 var node = (CSharpSyntaxNode)decl.GetSyntax();
                 var lineCounts = node.Accept(new AstLineCounter());
-                trapFile.numlines(callable, lineCounts);
+                if (lineCounts is object)
+                {
+                    trapFile.numlines(callable, lineCounts);
+                }
             }
         }
 
@@ -110,7 +114,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 if (IsSourceDeclaration)
                 {
                     foreach (var syntax in Symbol.DeclaringSyntaxReferences.Select(d => d.GetSyntax()).OfType<MethodDeclarationSyntax>())
-                        TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier.Name, this, explicitInterface);
+                        TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
                 }
             }
 
@@ -128,7 +132,7 @@ namespace Semmle.Extraction.CSharp.Entities
             m.Symbol.ReturnType.BuildOrWriteId(m.Context, trapFile, m.Symbol);
             trapFile.Write(" ");
 
-            trapFile.WriteSubId(m.ContainingType);
+            trapFile.WriteSubId(m.ContainingType!);
 
             AddExplicitInterfaceQualifierToId(m.Context, trapFile, m.Symbol.ExplicitInterfaceImplementations);
 
@@ -189,7 +193,7 @@ namespace Semmle.Extraction.CSharp.Entities
             var index = 0;
 
             var @params = method.MethodKind == MethodKind.ReducedExtension
-                ? method.ReducedFrom.Parameters
+                ? method.ReducedFrom!.Parameters
                 : method.Parameters;
 
             foreach (var param in @params)
@@ -232,7 +236,8 @@ namespace Semmle.Extraction.CSharp.Entities
         /// <param name="cx"></param>
         /// <param name="methodDecl"></param>
         /// <returns></returns>
-        public static Method Create(Context cx, IMethodSymbol methodDecl)
+        [return: NotNullIfNotNull("methodDecl")]
+        public static Method? Create(Context cx, IMethodSymbol? methodDecl)
         {
             if (methodDecl == null)
                 return null;
@@ -278,10 +283,10 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public Method OriginalDefinition =>
             IsReducedExtension
-                ? Create(Context, Symbol.ReducedFrom)
+                ? Create(Context, Symbol.ReducedFrom!)
                 : Create(Context, Symbol.OriginalDefinition);
 
-        public override Microsoft.CodeAnalysis.Location FullLocation => ReportingLocation;
+        public override Location? FullLocation => ReportingLocation;
 
         public override bool IsSourceDeclaration => Symbol.IsSourceDeclaration();
 

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

@@ -8,7 +8,7 @@ namespace Semmle.Extraction.CSharp.Entities
         private Modifier(Context cx, string init)
             : base(cx, init) { }
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => null;
+        public override Location? ReportingLocation => null;
 
         public override void WriteId(TextWriter trapFile)
         {

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

@@ -8,7 +8,7 @@ namespace Semmle.Extraction.CSharp.Entities
         private Namespace(Context cx, INamespaceSymbol init)
             : base(cx, init) { }
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => null;
+        public override Location? ReportingLocation => null;
 
         public override void Populate(TextWriter trapFile)
         {
@@ -49,7 +49,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         private string QualifiedName => Symbol.ToDisplayString();
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return obj is Namespace ns && QualifiedName == ns.QualifiedName;
         }

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

@@ -28,7 +28,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override void Populate(TextWriter trapFile)
         {
-            var @namespace = (INamespaceSymbol)Context.GetModel(node).GetSymbolInfo(node.Name).Symbol;
+            var @namespace = (INamespaceSymbol)Context.GetModel(node).GetSymbolInfo(node.Name).Symbol!;
             var ns = Namespace.Create(Context, @namespace);
             trapFile.namespace_declarations(this, ns);
             trapFile.namespace_declaration_location(this, Context.CreateLocation(node.Name.GetLocation()));

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

@@ -5,8 +5,7 @@ namespace Semmle.Extraction.CSharp.Entities
 {
     internal class NonGeneratedSourceLocation : Extraction.Entities.SourceLocation
     {
-        // todo: this can be changed to an override after the .NET 5 upgrade
-        private new Context Context => (Context)base.Context;
+        public override Context Context => (Context)base.Context;
 
         protected NonGeneratedSourceLocation(Context cx, Location init)
             : base(cx, init)

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

@@ -30,7 +30,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             PopulateMethod(trapFile);
             PopulateModifiers(trapFile);
-            ContainingType.PopulateGenerics();
+            ContainingType!.PopulateGenerics();
 
             var returnType = Type.Create(Context, Symbol.ReturnType);
             trapFile.methods(this, Name, ContainingType, returnType.TypeRef, OriginalDefinition);

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

@@ -9,10 +9,10 @@ namespace Semmle.Extraction.CSharp.Entities
 {
     internal class Parameter : CachedSymbol<IParameterSymbol>, IExpressionParentEntity
     {
-        protected IEntity Parent { get; set; }
+        protected IEntity? Parent { get; set; }
         protected Parameter Original { get; }
 
-        protected Parameter(Context cx, IParameterSymbol init, IEntity parent, Parameter original)
+        protected Parameter(Context cx, IParameterSymbol init, IEntity? parent, Parameter? original)
             : base(cx, init)
         {
             Parent = parent;
@@ -67,7 +67,7 @@ namespace Semmle.Extraction.CSharp.Entities
             }
         }
 
-        public static Parameter Create(Context cx, IParameterSymbol param, IEntity parent, Parameter original = null) =>
+        public static Parameter Create(Context cx, IParameterSymbol param, IEntity parent, Parameter? original = null) =>
             ParameterFactory.Instance.CreateEntity(cx, param, (param, parent, original));
 
         public static Parameter Create(Context cx, IParameterSymbol param) =>
@@ -77,6 +77,10 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             if (Parent == null)
                 Parent = Method.Create(Context, Symbol.ContainingSymbol as IMethodSymbol);
+
+            if (Parent == null)
+                throw new InternalError(Symbol, "Couldn't get parent of symbol.");
+
             trapFile.WriteSubId(Parent);
             trapFile.Write('_');
             trapFile.Write(Ordinal);
@@ -107,7 +111,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 Context.ModelError(Symbol, "Inconsistent parameter declaration");
 
             var type = Type.Create(Context, Symbol.Type);
-            trapFile.@params(this, Name, type.TypeRef, Ordinal, ParamKind, Parent, Original);
+            trapFile.@params(this, Name, type.TypeRef, Ordinal, ParamKind, Parent!, Original);
 
             foreach (var l in Symbol.Locations)
                 trapFile.param_location(this, Context.CreateLocation(l));
@@ -132,7 +136,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     .OfType<ParameterSyntax>()
                     .Where(s => s.Type != null))
                 {
-                    TypeMention.Create(Context, syntax.Type, this, type);
+                    TypeMention.Create(Context, syntax.Type!, this, type);
                 }
             }
 
@@ -151,7 +155,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     if (method != null)
                     {
                         var i = method.Parameters.IndexOf(Symbol);
-                        var indexer = (IPropertySymbol)method.AssociatedSymbol;
+                        var indexer = (IPropertySymbol?)method.AssociatedSymbol;
                         if (indexer != null)
                             defaultValue = GetParameterDefaultValue(indexer.Parameters[i]);
                     }
@@ -171,17 +175,17 @@ namespace Semmle.Extraction.CSharp.Entities
 
         bool IExpressionParentEntity.IsTopLevelParent => true;
 
-        private static EqualsValueClauseSyntax GetParameterDefaultValue(IParameterSymbol parameter)
+        private static EqualsValueClauseSyntax? GetParameterDefaultValue(IParameterSymbol parameter)
         {
             var syntax = parameter.DeclaringSyntaxReferences.Select(@ref => @ref.GetSyntax()).OfType<ParameterSyntax>().FirstOrDefault();
             return syntax?.Default;
         }
 
-        private class ParameterFactory : CachedEntityFactory<(IParameterSymbol, IEntity, Parameter), Parameter>
+        private class ParameterFactory : CachedEntityFactory<(IParameterSymbol, IEntity?, Parameter?), Parameter>
         {
             public static ParameterFactory Instance { get; } = new ParameterFactory();
 
-            public override Parameter Create(Context cx, (IParameterSymbol, IEntity, Parameter) init) => new Parameter(cx, init.Item1, init.Item2, init.Item3);
+            public override Parameter Create(Context cx, (IParameterSymbol, IEntity?, Parameter?) init) => new Parameter(cx, init.Item1, init.Item2, init.Item3);
         }
 
         public override TrapStackBehaviour TrapStackBehaviour => TrapStackBehaviour.OptionalLabel;
@@ -211,42 +215,44 @@ namespace Semmle.Extraction.CSharp.Entities
             return 98735267;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return obj != null && obj.GetType() == typeof(VarargsType);
         }
 
         public static VarargsType Create(Context cx) => VarargsTypeFactory.Instance.CreateEntity(cx, typeof(VarargsType), null);
 
-        private class VarargsTypeFactory : CachedEntityFactory<string, VarargsType>
+        private class VarargsTypeFactory : CachedEntityFactory<string?, VarargsType>
         {
             public static VarargsTypeFactory Instance { get; } = new VarargsTypeFactory();
 
-            public override VarargsType Create(Context cx, string init) => new VarargsType(cx);
+            public override VarargsType Create(Context cx, string? init) => new VarargsType(cx);
         }
     }
 
     internal class VarargsParam : Parameter
     {
+#nullable disable warnings
         private VarargsParam(Context cx, Method methodKey)
             : base(cx, null, methodKey, null) { }
+#nullable restore warnings
 
         public override void Populate(TextWriter trapFile)
         {
             var typeKey = VarargsType.Create(Context);
             // !! Maybe originaldefinition is wrong
-            trapFile.@params(this, "", typeKey, Ordinal, Kind.None, Parent, this);
+            trapFile.@params(this, "", typeKey, Ordinal, Kind.None, Parent!, this);
             trapFile.param_location(this, GeneratedLocation.Create(Context));
         }
 
-        protected override int Ordinal => ((Method)Parent).OriginalDefinition.Symbol.Parameters.Length;
+        protected override int Ordinal => ((Method)Parent!).OriginalDefinition.Symbol.Parameters.Length;
 
         public override int GetHashCode()
         {
             return 9873567;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return obj != null && obj.GetType() == typeof(VarargsParam);
         }
@@ -268,18 +274,18 @@ namespace Semmle.Extraction.CSharp.Entities
         private ConstructedExtensionParameter(Context cx, Method method, Parameter original)
             : base(cx, original.Symbol, method, original)
         {
-            constructedType = method.Symbol.ReceiverType;
+            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.@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));
+            ExtensionParamFactory.Instance.CreateEntity(cx, (new SymbolEqualityWrapper(parameter.Symbol), new SymbolEqualityWrapper(method.Symbol.ReceiverType!)), (method, parameter));
 
         private class ExtensionParamFactory : CachedEntityFactory<(Method, Parameter), ConstructedExtensionParameter>
         {

csharp/extractor/Semmle.Extraction.CSharp/Entities/PreprocessorDirectives/LineDirective.cs

@@ -26,7 +26,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
             if (trivia.Line.IsKind(SyntaxKind.NumericLiteralToken))
             {
-                var value = (int)trivia.Line.Value;
+                var value = (int)trivia.Line.Value!;
                 trapFile.directive_line_value(this, value);
 
                 if (!string.IsNullOrWhiteSpace(trivia.File.ValueText))

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

@@ -25,7 +25,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             trapFile.WriteSubId(Type);
             trapFile.Write(" ");
-            trapFile.WriteSubId(ContainingType);
+            trapFile.WriteSubId(ContainingType!);
             trapFile.Write('.');
             Method.AddExplicitInterfaceQualifierToId(Context, trapFile, Symbol.ExplicitInterfaceImplementations);
             trapFile.Write(Symbol.Name);
@@ -42,7 +42,7 @@ namespace Semmle.Extraction.CSharp.Entities
             PopulateRefKind(trapFile, Symbol.RefKind);
 
             var type = Type;
-            trapFile.properties(this, Symbol.GetName(), ContainingType, type.TypeRef, Create(Context, Symbol.OriginalDefinition));
+            trapFile.properties(this, Symbol.GetName(), ContainingType!, type.TypeRef, Create(Context, Symbol.OriginalDefinition));
 
             var getter = Symbol.GetMethod;
             var setter = Symbol.SetMethod;
@@ -63,7 +63,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 trapFile.explicitly_implements(this, explicitInterface.TypeRef);
 
                 foreach (var syntax in declSyntaxReferences)
-                    TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier.Name, this, explicitInterface);
+                    TypeMention.Create(Context, syntax.ExplicitInterfaceSpecifier!.Name, this, explicitInterface);
             }
 
             foreach (var l in Locations)
@@ -84,7 +84,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 {
                     Context.PopulateLater(() =>
                     {
-                        var loc = Context.CreateLocation(initializer.GetLocation());
+                        var loc = Context.CreateLocation(initializer!.GetLocation());
                         var annotatedType = AnnotatedTypeSymbol.CreateNotAnnotated(Symbol.Type);
                         var simpleAssignExpr = new Expression(new ExpressionInfo(Context, annotatedType, loc, ExprKind.SIMPLE_ASSIGN, this, child++, false, null));
                         Expression.CreateFromNode(new ExpressionNodeInfo(Context, initializer.Value, simpleAssignExpr, 0));

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/Catch.cs

@@ -15,16 +15,16 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
         protected override void PopulateStatement(TextWriter trapFile)
         {
             var isSpecificCatchClause = Stmt.Declaration != null;
-            var hasVariableDeclaration = isSpecificCatchClause && Stmt.Declaration.Identifier.RawKind != 0;
+            var hasVariableDeclaration = isSpecificCatchClause && Stmt.Declaration!.Identifier.RawKind != 0;
 
             if (hasVariableDeclaration) // A catch clause of the form 'catch(Ex ex) { ... }'
             {
-                var decl = Expressions.VariableDeclaration.Create(Context, Stmt.Declaration, false, this, 0);
+                var decl = Expressions.VariableDeclaration.Create(Context, Stmt.Declaration!, false, this, 0);
                 trapFile.catch_type(this, Type.Create(Context, decl.Type).TypeRef, true);
             }
             else if (isSpecificCatchClause) // A catch clause of the form 'catch(Ex) { ... }'
             {
-                trapFile.catch_type(this, Type.Create(Context, Context.GetType(Stmt.Declaration.Type)).TypeRef, true);
+                trapFile.catch_type(this, Type.Create(Context, Context.GetType(Stmt.Declaration!.Type)).TypeRef, true);
             }
             else // A catch clause of the form 'catch { ... }'
             {

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/ForEach.cs

@@ -32,7 +32,7 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             Expression.Create(Context, Stmt.Expression, this, 1);
 
             var semanticModel = Context.GetModel(Stmt);
-            var typeSymbol = semanticModel.GetDeclaredSymbol(Stmt);
+            var typeSymbol = semanticModel.GetDeclaredSymbol(Stmt)!;
             var type = typeSymbol.GetAnnotatedType();
 
             var location = Context.CreateLocation(Stmt.Identifier.GetLocation());

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/GlobalStatementsBlock.cs

@@ -15,7 +15,7 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             this.parent = parent;
         }
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation
         {
             get
             {

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/Goto.cs

@@ -36,12 +36,12 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             switch (GetKind(Stmt))
             {
                 case StmtKind.GOTO:
-                    var target = ((IdentifierNameSyntax)Stmt.Expression).Identifier.Text;
+                    var target = ((IdentifierNameSyntax)Stmt.Expression!).Identifier.Text;
                     trapFile.exprorstmt_name(this, target);
                     break;
                 case StmtKind.GOTO_CASE:
-                    Expr = Expression.Create(Context, Stmt.Expression, this, 0);
-                    ConstantValue = Switch.LabelForValue(Context.GetModel(Stmt).GetConstantValue(Stmt.Expression).Value);
+                    Expr = Expression.Create(Context, Stmt.Expression!, this, 0);
+                    ConstantValue = Switch.LabelForValue(Context.GetModel(Stmt).GetConstantValue(Stmt.Expression!).Value);
                     break;
                 case StmtKind.GOTO_DEFAULT:
                     ConstantValue = Switch.DefaultLabel;
@@ -49,9 +49,9 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             }
         }
 
-        public Expression Expr { get; private set; }
+        public Expression? Expr { get; private set; }
 
-        public object ConstantValue { get; private set; }
+        public object? ConstantValue { get; private set; }
 
         public bool IsDefault => ConstantValue == Switch.DefaultLabel;
     }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/Labeled.cs

@@ -8,7 +8,7 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
     {
         private readonly IStatementParentEntity parent;
         private readonly int child;
-        private Statement labelledStmt;
+        private Statement? labelledStmt;
 
         private Labeled(Context cx, LabeledStatementSyntax stmt, IStatementParentEntity parent, int child)
             : base(cx, stmt, StmtKind.LABEL, parent, child)
@@ -33,6 +33,6 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             labelledStmt = Statement.Create(Context, Stmt.Statement, parent, child + 1);
         }
 
-        public override int NumberOfStatements => 1 + labelledStmt.NumberOfStatements;
+        public override int NumberOfStatements => 1 + labelledStmt?.NumberOfStatements ?? 0;
     }
 }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/LocalFunction.cs

@@ -22,7 +22,7 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
         /// <summary>
         /// Gets the IMethodSymbol for this local function statement.
         /// </summary>
-        private IMethodSymbol Symbol
+        private IMethodSymbol? Symbol
         {
             get
             {
@@ -31,14 +31,16 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             }
         }
 
-        /// <summary>
-        /// Gets the function defined by this local statement.
-        /// </summary>
-        private Entities.LocalFunction Function => Entities.LocalFunction.Create(Context, Symbol);
-
         protected override void PopulateStatement(TextWriter trapFile)
         {
-            trapFile.local_function_stmts(this, Function);
+            if (Symbol is null)
+            {
+                Context.ExtractionError("Could not get local function symbol", null, Context.CreateLocation(this.ReportingLocation), severity: Util.Logging.Severity.Warning);
+                return;
+            }
+
+            var function = Entities.LocalFunction.Create(Context, Symbol);
+            trapFile.local_function_stmts(this, function);
         }
     }
 }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/Switch.cs

@@ -13,7 +13,7 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
         // Sometimes, the literal "null" is used as a label.
         // This is inconveniently represented by the "null" object.
         // This cannot be stored in a Dictionary<>, so substitute an object which can be.
-        public static object LabelForValue(object label)
+        public static object LabelForValue(object? label)
         {
             return label ?? nullLabel;
         }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/Try.cs

@@ -32,17 +32,5 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
                 Create(Context, Stmt.Finally.Block, this, -1);
             }
         }
-
-        public static SyntaxNodeOrToken NextNode(SyntaxNode node)
-        {
-            for (var i = node.Parent.ChildNodesAndTokens().GetEnumerator(); i.MoveNext();)
-            {
-                if (i.Current == node)
-                {
-                    return i.MoveNext() ? i.Current : null;
-                }
-            }
-            return null;
-        }
     }
 }

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

@@ -12,9 +12,9 @@ namespace Semmle.Extraction.CSharp.Entities
         private readonly TypeSyntax syntax;
         private readonly IEntity parent;
         private readonly Type type;
-        private readonly Microsoft.CodeAnalysis.Location loc;
+        private readonly Microsoft.CodeAnalysis.Location? loc;
 
-        private TypeMention(Context cx, TypeSyntax syntax, IEntity parent, Type type, Microsoft.CodeAnalysis.Location loc = null)
+        private TypeMention(Context cx, TypeSyntax syntax, IEntity parent, Type type, Microsoft.CodeAnalysis.Location? loc = null)
             : base(cx)
         {
             this.syntax = syntax;
@@ -32,7 +32,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 case NullableTypeSyntax nts:
                     // int[]? -> int[] -> int
                     // int?   -> int?
-                    return Context.GetTypeInfo(nts.ElementType).Type.IsReferenceType
+                    return Context.GetTypeInfo(nts.ElementType).Type?.IsReferenceType == true
                         ? GetArrayElementType(nts.ElementType)
                         : nts;
                 case PointerTypeSyntax pts:
@@ -121,14 +121,14 @@ namespace Semmle.Extraction.CSharp.Entities
             trapFile.type_mention_location(this, Context.CreateLocation(loc));
         }
 
-        public static TypeMention Create(Context cx, TypeSyntax syntax, IEntity parent, Type type, Microsoft.CodeAnalysis.Location loc = null)
+        public static TypeMention Create(Context cx, TypeSyntax syntax, IEntity parent, Type type, Microsoft.CodeAnalysis.Location? loc = null)
         {
             var ret = new TypeMention(cx, syntax, parent, type, loc);
             cx.Try(syntax, null, () => ret.Populate(cx.TrapWriter.Writer));
             return ret;
         }
 
-        public static TypeMention Create(Context cx, TypeSyntax syntax, IEntity parent, AnnotatedTypeSymbol? type, Microsoft.CodeAnalysis.Location loc = null) =>
+        public static TypeMention Create(Context cx, TypeSyntax syntax, IEntity parent, AnnotatedTypeSymbol? type, Microsoft.CodeAnalysis.Location? loc = null) =>
             Create(cx, syntax, parent, Type.Create(cx, type?.Symbol), loc);
 
         public override TrapStackBehaviour TrapStackBehaviour => TrapStackBehaviour.OptionalLabel;

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/DynamicType.cs

@@ -11,7 +11,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public static DynamicType Create(Context cx, IDynamicTypeSymbol type) => DynamicTypeFactory.Instance.CreateEntityFromSymbol(cx, type);
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => Context.Compilation.ObjectType.Locations.FirstOrDefault();
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => Context.Compilation.ObjectType.Locations.FirstOrDefault();
 
         public override void Populate(TextWriter trapFile)
         {

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs

@@ -36,7 +36,7 @@ namespace Semmle.Extraction.CSharp.Entities
         {
             if (Symbol.TypeKind == TypeKind.Error)
             {
-                Context.Extractor.MissingType(Symbol.ToString(), Context.FromSource);
+                Context.Extractor.MissingType(Symbol.ToString()!, Context.FromSource);
                 return;
             }
 
@@ -108,7 +108,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 foreach (var l in GetLocations(Symbol))
                     yield return Context.CreateLocation(l);
 
-                if (Context.Extractor.OutputPath != null && Symbol.DeclaringSyntaxReferences.Any())
+                if (!Context.Extractor.Standalone && Symbol.DeclaringSyntaxReferences.Any())
                     yield return Assembly.CreateOutputAssembly(Context);
             }
         }
@@ -124,7 +124,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 );
         }
 
-        public override Microsoft.CodeAnalysis.Location ReportingLocation => GetLocations(Symbol).FirstOrDefault();
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => GetLocations(Symbol).FirstOrDefault();
 
         private bool IsAnonymousType() => Symbol.IsAnonymousType || Symbol.Name.Contains("__AnonymousType");
 

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NullType.cs

@@ -22,18 +22,18 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override int GetHashCode() => 987354;
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return obj != null && obj.GetType() == typeof(NullType);
         }
 
         public static Type Create(Context cx) => NullTypeFactory.Instance.CreateEntity(cx, typeof(NullType), null);
 
-        private class NullTypeFactory : CachedEntityFactory<ITypeSymbol, NullType>
+        private class NullTypeFactory : CachedEntityFactory<ITypeSymbol?, NullType>
         {
             public static NullTypeFactory Instance { get; } = new NullTypeFactory();
 
-            public override NullType Create(Context cx, ITypeSymbol init) => new NullType(cx);
+            public override NullType Create(Context cx, ITypeSymbol? init) => new NullType(cx);
         }
     }
 }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/Nullability.cs

@@ -64,7 +64,7 @@ namespace Semmle.Extraction.CSharp.Entities
             NullableParameters = method.GetAnnotatedTypeArguments().Select(a => new Nullability(a)).ToArray();
         }
 
-        public override bool Equals(object other)
+        public override bool Equals(object? other)
         {
             return other is Nullability n && Annotation == n.Annotation && NullableParameters.SequenceEqual(n.NullableParameters);
         }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/Type.cs

@@ -10,9 +10,10 @@ namespace Semmle.Extraction.CSharp.Entities
 {
     internal abstract class Type : CachedSymbol<ITypeSymbol>
     {
-        protected Type(Context cx, ITypeSymbol init)
+#nullable disable warnings
+        protected Type(Context cx, ITypeSymbol? init)
             : base(cx, init) { }
-
+#nullable restore warnings
 
         public override bool NeedsPopulation =>
             base.NeedsPopulation || Symbol.TypeKind == TypeKind.Dynamic || Symbol.TypeKind == TypeKind.TypeParameter;
@@ -132,7 +133,7 @@ namespace Semmle.Extraction.CSharp.Entities
             {
                 // This is a delegate.
                 // The method "Invoke" has the return type.
-                var invokeMethod = ((INamedTypeSymbol)Symbol).DelegateInvokeMethod;
+                var invokeMethod = ((INamedTypeSymbol)Symbol).DelegateInvokeMethod!;
                 ExtractParametersForDelegateLikeType(trapFile, invokeMethod,
                     t => trapFile.delegate_return_type(this, t));
             }
@@ -155,7 +156,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
                 baseLists
                     .Where(bl => bl != null)
-                    .SelectMany(bl => bl.Types)
+                    .SelectMany(bl => bl!.Types)
                     .Zip(
                         baseTypes.Where(bt => bt.Symbol.SpecialType != SpecialType.System_Object),
                         (s, t) => TypeMention.Create(Context, s.Type, this, t))
@@ -258,7 +259,7 @@ namespace Semmle.Extraction.CSharp.Entities
             ExtractRecursive();
         }
 
-        public static Type Create(Context cx, ITypeSymbol type)
+        public static Type Create(Context cx, ITypeSymbol? type)
         {
             type = type.DisambiguateType();
             return type == null
@@ -271,7 +272,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public virtual int Dimension => 0;
 
-        public static bool IsDelegate(ITypeSymbol symbol) =>
+        public static bool IsDelegate(ITypeSymbol? symbol) =>
             symbol != null && symbol.TypeKind == TypeKind.Delegate;
 
         /// <summary>
@@ -279,19 +280,19 @@ namespace Semmle.Extraction.CSharp.Entities
         /// </summary>
         private class DelegateTypeParameter : Parameter
         {
-            private DelegateTypeParameter(Context cx, IParameterSymbol init, IEntity parent, Parameter original)
+            private DelegateTypeParameter(Context cx, IParameterSymbol init, IEntity parent, Parameter? original)
                 : base(cx, init, parent, original) { }
 
-            public static new DelegateTypeParameter Create(Context cx, IParameterSymbol param, IEntity parent, Parameter original = null) =>
+            public static new DelegateTypeParameter Create(Context cx, IParameterSymbol param, IEntity parent, Parameter? original = null) =>
                // We need to use a different cache key than `param` to avoid mixing up
                // `DelegateTypeParameter`s and `Parameter`s
                DelegateTypeParameterFactory.Instance.CreateEntity(cx, (typeof(DelegateTypeParameter), new SymbolEqualityWrapper(param)), (param, parent, original));
 
-            private class DelegateTypeParameterFactory : CachedEntityFactory<(IParameterSymbol, IEntity, Parameter), DelegateTypeParameter>
+            private class DelegateTypeParameterFactory : CachedEntityFactory<(IParameterSymbol, IEntity, Parameter?), DelegateTypeParameter>
             {
                 public static DelegateTypeParameterFactory Instance { get; } = new DelegateTypeParameterFactory();
 
-                public override DelegateTypeParameter Create(Context cx, (IParameterSymbol, IEntity, Parameter) init) =>
+                public override DelegateTypeParameter Create(Context cx, (IParameterSymbol, IEntity, Parameter?) init) =>
                     new DelegateTypeParameter(cx, init.Item1, init.Item2, init.Item3);
             }
         }
@@ -312,7 +313,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public override TrapStackBehaviour TrapStackBehaviour => TrapStackBehaviour.NoLabel;
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             var other = obj as Type;
             return other?.GetType() == GetType() && SymbolEqualityComparer.Default.Equals(other.Symbol, Symbol);
@@ -326,7 +327,6 @@ namespace Semmle.Extraction.CSharp.Entities
         protected Type(Context cx, T init)
             : base(cx, init) { }
 
-        // todo: change this with .net 5 to be an override
         public new T Symbol => (T)base.Symbol;
     }
 }

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/TypeParameter.cs

@@ -63,7 +63,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     .Select(d => d.GetSyntax())
                     .Select(s => s.Parent)
                     .Where(p => p != null)
-                    .Select(p => p.Parent)
+                    .Select(p => p!.Parent)
                     .ToArray();
                 var clauses = declSyntaxReferences.OfType<MethodDeclarationSyntax>().SelectMany(m => m.ConstraintClauses);
                 clauses = clauses.Concat(declSyntaxReferences.OfType<ClassDeclarationSyntax>().SelectMany(c => c.ConstraintClauses));

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

@@ -42,7 +42,7 @@ namespace Semmle.Extraction.CSharp.Entities
             else
             {
                 // A "using static"
-                var m = Type.Create(Context, (ITypeSymbol)info.Symbol);
+                var m = Type.Create(Context, (ITypeSymbol?)info.Symbol);
                 trapFile.using_static_directives(this, m.TypeRef);
                 trapFile.using_directive_location(this, Context.CreateLocation(ReportingLocation));
             }

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Analyser.cs

@@ -0,0 +1,311 @@
+using System;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using System.IO;
+using System.Linq;
+using Semmle.Extraction.CSharp.Populators;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using System.Diagnostics;
+using Semmle.Util.Logging;
+
+namespace Semmle.Extraction.CSharp
+{
+    /// <summary>
+    /// Encapsulates a C# analysis task.
+    /// </summary>
+    public class Analyser : IDisposable
+    {
+        protected Extraction.Extractor? extractor;
+        protected CSharpCompilation? compilation;
+        protected Layout? layout;
+        protected CommonOptions? options;
+
+        private readonly object progressMutex = new object();
+
+        // The bulk of the extraction work, potentially executed in parallel.
+        protected readonly List<Action> extractionTasks = new List<Action>();
+        private int taskCount = 0;
+
+        private readonly Stopwatch stopWatch = new Stopwatch();
+
+        private readonly IProgressMonitor progressMonitor;
+
+        public ILogger Logger { get; }
+
+        protected readonly bool addAssemblyTrapPrefix;
+
+        public PathTransformer PathTransformer { get; }
+
+        protected Analyser(IProgressMonitor pm, ILogger logger, bool addAssemblyTrapPrefix, PathTransformer pathTransformer)
+        {
+            Logger = logger;
+            this.addAssemblyTrapPrefix = addAssemblyTrapPrefix;
+            Logger.Log(Severity.Info, "EXTRACTION STARTING at {0}", DateTime.Now);
+            stopWatch.Start();
+            progressMonitor = pm;
+            PathTransformer = pathTransformer;
+        }
+
+        /// <summary>
+        /// Perform an analysis on a source file/syntax tree.
+        /// </summary>
+        /// <param name="tree">Syntax tree to analyse.</param>
+        public void AnalyseTree(SyntaxTree tree)
+        {
+            extractionTasks.Add(() => DoExtractTree(tree));
+        }
+
+#nullable disable warnings
+
+        /// <summary>
+        ///     Enqueue all reference analysis tasks.
+        /// </summary>
+        public void AnalyseReferences()
+        {
+            foreach (var assembly in compilation.References.OfType<PortableExecutableReference>())
+            {
+                // CIL first - it takes longer.
+                if (options.CIL)
+                    extractionTasks.Add(() => DoExtractCIL(assembly));
+                extractionTasks.Add(() => DoAnalyseReferenceAssembly(assembly));
+            }
+        }
+
+        /// <summary>
+        ///     Constructs the map from assembly string to its filename.
+        ///
+        ///     Roslyn doesn't record the relationship between a filename and its assembly
+        ///     information, so we need to retrieve this information manually.
+        /// </summary>
+        protected void SetReferencePaths()
+        {
+            foreach (var reference in compilation.References.OfType<PortableExecutableReference>())
+            {
+                try
+                {
+                    var refPath = reference.FilePath!;
+
+                    /*  This method is significantly faster and more lightweight than using
+                     *  System.Reflection.Assembly.ReflectionOnlyLoadFrom. It is also allows
+                     *  loading the same assembly from different locations.
+                     */
+                    using var pereader = new System.Reflection.PortableExecutable.PEReader(new FileStream(refPath, FileMode.Open, FileAccess.Read, FileShare.Read));
+
+                    var metadata = pereader.GetMetadata();
+                    string assemblyIdentity;
+                    unsafe
+                    {
+                        var reader = new System.Reflection.Metadata.MetadataReader(metadata.Pointer, metadata.Length);
+                        var def = reader.GetAssemblyDefinition();
+                        assemblyIdentity = reader.GetString(def.Name) + " " + def.Version;
+                    }
+                    extractor.SetAssemblyFile(assemblyIdentity, refPath);
+
+                }
+                catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
+                {
+                    extractor.Message(new Message("Exception reading reference file", reference.FilePath, null, ex.StackTrace));
+                }
+            }
+        }
+
+        /// <summary>
+        ///     Extract an assembly to a new trap file.
+        ///     If the trap file exists, skip extraction to avoid duplicating
+        ///     extraction within the snapshot.
+        /// </summary>
+        /// <param name="r">The assembly to extract.</param>
+        private void DoAnalyseReferenceAssembly(PortableExecutableReference r)
+        {
+            try
+            {
+                var stopwatch = new Stopwatch();
+                stopwatch.Start();
+
+                var assemblyPath = r.FilePath!;
+                var transformedAssemblyPath = PathTransformer.Transform(assemblyPath);
+                var projectLayout = layout.LookupProjectOrDefault(transformedAssemblyPath);
+                using var trapWriter = projectLayout.CreateTrapWriter(Logger, transformedAssemblyPath, options.TrapCompression, discardDuplicates: true);
+
+                var skipExtraction = options.Cache && File.Exists(trapWriter.TrapFile);
+
+                if (!skipExtraction)
+                {
+                    /* Note on parallel builds:
+                     *
+                     * The trap writer and source archiver both perform atomic moves
+                     * of the file to the final destination.
+                     *
+                     * If the same source file or trap file are generated concurrently
+                     * (by different parallel invocations of the extractor), then
+                     * last one wins.
+                     *
+                     * Specifically, if two assemblies are analysed concurrently in a build,
+                     * then there is a small amount of duplicated work but the output should
+                     * still be correct.
+                     */
+
+                    // compilation.Clone() reduces memory footprint by allowing the symbols
+                    // in c to be garbage collected.
+                    Compilation c = compilation.Clone();
+
+
+                    if (c.GetAssemblyOrModuleSymbol(r) is IAssemblySymbol assembly)
+                    {
+                        var cx = new Context(extractor, c, trapWriter, new AssemblyScope(assembly, assemblyPath), addAssemblyTrapPrefix);
+
+                        foreach (var module in assembly.Modules)
+                        {
+                            AnalyseNamespace(cx, module.GlobalNamespace);
+                        }
+
+                        Entities.Attribute.ExtractAttributes(cx, assembly, Entities.Assembly.Create(cx, assembly.GetSymbolLocation()));
+
+                        cx.PopulateAll();
+                    }
+                }
+
+                ReportProgress(assemblyPath, trapWriter.TrapFile, stopwatch.Elapsed, skipExtraction ? AnalysisAction.UpToDate : AnalysisAction.Extracted);
+            }
+            catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
+            {
+                Logger.Log(Severity.Error, "  Unhandled exception analyzing {0}: {1}", r.FilePath, ex);
+            }
+        }
+
+        private void DoExtractCIL(PortableExecutableReference r)
+        {
+            var stopwatch = new Stopwatch();
+            stopwatch.Start();
+            CIL.Analyser.ExtractCIL(layout, r.FilePath!, Logger, !options.Cache, options.PDB, options.TrapCompression, out var trapFile, out var extracted);
+            stopwatch.Stop();
+            ReportProgress(r.FilePath, trapFile, stopwatch.Elapsed, extracted ? AnalysisAction.Extracted : AnalysisAction.UpToDate);
+        }
+
+        private void DoExtractTree(SyntaxTree tree)
+        {
+            try
+            {
+                var stopwatch = new Stopwatch();
+                stopwatch.Start();
+                var sourcePath = tree.FilePath;
+                var transformedSourcePath = PathTransformer.Transform(sourcePath);
+
+                var projectLayout = layout.LookupProjectOrNull(transformedSourcePath);
+                var excluded = projectLayout == null;
+                var trapPath = excluded ? "" : projectLayout!.GetTrapPath(Logger, transformedSourcePath, options.TrapCompression);
+                var upToDate = false;
+
+                if (!excluded)
+                {
+                    // compilation.Clone() is used to allow symbols to be garbage collected.
+                    using var trapWriter = projectLayout!.CreateTrapWriter(Logger, transformedSourcePath, options.TrapCompression, discardDuplicates: false);
+
+                    upToDate = options.Fast && FileIsUpToDate(sourcePath, trapWriter.TrapFile);
+
+                    if (!upToDate)
+                    {
+                        var cx = new Context(extractor, compilation.Clone(), trapWriter, new SourceScope(tree), addAssemblyTrapPrefix);
+                        // Ensure that the file itself is populated in case the source file is totally empty
+                        var root = tree.GetRoot();
+                        Entities.File.Create(cx, root.SyntaxTree.FilePath);
+
+                        var csNode = (CSharpSyntaxNode)root;
+                        csNode.Accept(new CompilationUnitVisitor(cx));
+                        csNode.Accept(new DirectiveVisitor(cx));
+                        cx.PopulateAll();
+                        CommentPopulator.ExtractCommentBlocks(cx, cx.CommentGenerator);
+                        cx.PopulateAll();
+                    }
+                }
+
+                ReportProgress(sourcePath, trapPath, stopwatch.Elapsed, excluded
+                    ? AnalysisAction.Excluded
+                    : upToDate
+                        ? AnalysisAction.UpToDate
+                        : AnalysisAction.Extracted);
+            }
+            catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
+            {
+                extractor.Message(new Message($"Unhandled exception processing syntax tree. {ex.Message}", tree.FilePath, null, ex.StackTrace));
+            }
+        }
+
+#nullable restore warnings
+
+        private static bool FileIsUpToDate(string src, string dest)
+        {
+            return File.Exists(dest) &&
+                File.GetLastWriteTime(dest) >= File.GetLastWriteTime(src);
+        }
+
+        private void AnalyseNamespace(Context cx, INamespaceSymbol ns)
+        {
+            foreach (var memberNamespace in ns.GetNamespaceMembers())
+            {
+                AnalyseNamespace(cx, memberNamespace);
+            }
+
+            foreach (var memberType in ns.GetTypeMembers())
+            {
+                Entities.Type.Create(cx, memberType).ExtractRecursive();
+            }
+        }
+
+        private void ReportProgress(string src, string output, TimeSpan time, AnalysisAction action)
+        {
+            lock (progressMutex)
+                progressMonitor.Analysed(++taskCount, extractionTasks.Count, src, output, time, action);
+        }
+
+        /// <summary>
+        /// Run all extraction tasks.
+        /// </summary>
+        /// <param name="numberOfThreads">The number of threads to use.</param>
+        public void PerformExtraction(int numberOfThreads)
+        {
+            Parallel.Invoke(
+                new ParallelOptions { MaxDegreeOfParallelism = numberOfThreads },
+                extractionTasks.ToArray());
+        }
+
+        public virtual void Dispose()
+        {
+            stopWatch.Stop();
+            Logger.Log(Severity.Info, "  Peak working set = {0} MB", Process.GetCurrentProcess().PeakWorkingSet64 / (1024 * 1024));
+
+            if (TotalErrors > 0)
+                Logger.Log(Severity.Info, "EXTRACTION FAILED with {0} error{1} in {2}", TotalErrors, TotalErrors == 1 ? "" : "s", stopWatch.Elapsed);
+            else
+                Logger.Log(Severity.Info, "EXTRACTION SUCCEEDED in {0}", stopWatch.Elapsed);
+
+            Logger.Dispose();
+        }
+
+        /// <summary>
+        /// Number of errors encountered during extraction.
+        /// </summary>
+        private int ExtractorErrors => extractor?.Errors ?? 0;
+
+        /// <summary>
+        /// Number of errors encountered by the compiler.
+        /// </summary>
+        public int CompilationErrors { get; set; }
+
+        /// <summary>
+        /// Total number of errors reported.
+        /// </summary>
+        public int TotalErrors => CompilationErrors + ExtractorErrors;
+
+        /// <summary>
+        /// Logs information about the extractor.
+        /// </summary>
+        public void LogExtractorInfo(string extractorVersion)
+        {
+            Logger.Log(Severity.Info, "  Extractor: {0}", Environment.GetCommandLineArgs().First());
+            Logger.Log(Severity.Info, "  Extractor version: {0}", extractorVersion);
+            Logger.Log(Severity.Info, "  Current working directory: {0}", Directory.GetCurrentDirectory());
+        }
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Extractor/AnalysisAction.cs

@@ -0,0 +1,12 @@
+namespace Semmle.Extraction.CSharp
+{
+    /// <summary>
+    /// What action was performed when extracting a file.
+    /// </summary>
+    public enum AnalysisAction
+    {
+        Extracted,
+        UpToDate,
+        Excluded
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Extractor/CompilerVersion.cs

@@ -14,12 +14,12 @@ namespace Semmle.Extraction.CSharp
     public class CompilerVersion
     {
         private const string csc_rsp = "csc.rsp";
-        private readonly string specifiedFramework = null;
+        private readonly string? specifiedFramework = null;
 
         /// <summary>
         /// The value specified by --compiler, or null.
         /// </summary>
-        public string SpecifiedCompiler
+        public string? SpecifiedCompiler
         {
             get;
             private set;
@@ -28,12 +28,20 @@ namespace Semmle.Extraction.CSharp
         /// <summary>
         /// Why was the candidate exe rejected as a compiler?
         /// </summary>
-        public string SkipReason
+        public string? SkipReason
         {
             get;
             private set;
         }
 
+        private static readonly Dictionary<string, string> knownCompilerNames = new Dictionary<string, string>
+        {
+            { "csc.exe", "Microsoft" },
+            { "csc2.exe", "Microsoft" },
+            { "csc.dll", "Microsoft" },
+            { "mcs.exe", "Novell" }
+        };
+
         /// <summary>
         /// Probes the compiler (if specified).
         /// </summary>
@@ -52,16 +60,13 @@ namespace Semmle.Extraction.CSharp
                 }
 
                 // Reads the file details from the .exe
-                var versionInfo = FileVersionInfo.GetVersionInfo(SpecifiedCompiler);
-
                 var compilerDir = Path.GetDirectoryName(SpecifiedCompiler);
-                var knownCompilerNames = new Dictionary<string, string>
+                if (compilerDir is null)
                 {
-                    { "csc.exe", "Microsoft" },
-                    { "csc2.exe", "Microsoft" },
-                    { "csc.dll", "Microsoft" },
-                    { "mcs.exe", "Novell" }
-                };
+                    SkipExtractionBecause("the compiler directory could not be retrieved");
+                    return;
+                }
+
                 var mscorlibExists = File.Exists(Path.Combine(compilerDir, "mscorlib.dll"));
 
                 if (specifiedFramework == null && mscorlibExists)
@@ -69,7 +74,8 @@ namespace Semmle.Extraction.CSharp
                     specifiedFramework = compilerDir;
                 }
 
-                if (!knownCompilerNames.TryGetValue(versionInfo.OriginalFilename, out var vendor))
+                var versionInfo = FileVersionInfo.GetVersionInfo(SpecifiedCompiler);
+                if (!knownCompilerNames.TryGetValue(versionInfo.OriginalFilename ?? string.Empty, out var vendor))
                 {
                     SkipExtractionBecause("the compiler name is not recognised");
                     return;
@@ -114,7 +120,7 @@ namespace Semmle.Extraction.CSharp
         /// <summary>
         /// Gets additional reference directories - the compiler directory.
         /// </summary>
-        public string AdditionalReferenceDirectories => SpecifiedCompiler != null ? Path.GetDirectoryName(SpecifiedCompiler) : null;
+        public string? AdditionalReferenceDirectories => SpecifiedCompiler != null ? Path.GetDirectoryName(SpecifiedCompiler) : null;
 
         /// <summary>
         /// Adds @csc.rsp to the argument list to mimic csc.exe.
@@ -134,6 +140,6 @@ namespace Semmle.Extraction.CSharp
             return args.Any(arg => new[] { "/noconfig", "-noconfig" }.Contains(arg.ToLowerInvariant()));
         }
 
-        public IEnumerable<string> ArgsWithResponse { get; }
+        public IEnumerable<string> ArgsWithResponse { get; } = Enumerable.Empty<string>();
     }
 }

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Context.cs

@@ -29,7 +29,7 @@ namespace Semmle.Extraction.CSharp
             return cachedModel;
         }
 
-        private SemanticModel cachedModel;
+        private SemanticModel? cachedModel;
 
         /// <summary>
         /// The current compilation unit.
@@ -51,7 +51,7 @@ namespace Semmle.Extraction.CSharp
 
         public bool IsAssemblyScope => scope is AssemblyScope;
 
-        private SyntaxTree SourceTree => scope is SourceScope sc ? sc.SourceTree : null;
+        private SyntaxTree? SourceTree => scope is SourceScope sc ? sc.SourceTree : null;
 
         /// <summary>
         ///     Whether the given symbol needs to be defined in this context.
@@ -85,7 +85,7 @@ namespace Semmle.Extraction.CSharp
                 : CreateLocation(Microsoft.CodeAnalysis.Location.Create(SourceTree, Microsoft.CodeAnalysis.Text.TextSpan.FromBounds(0, 0)));
         }
 
-        public override Extraction.Entities.Location CreateLocation(Microsoft.CodeAnalysis.Location location)
+        public override Extraction.Entities.Location CreateLocation(Microsoft.CodeAnalysis.Location? location)
         {
             return (location == null || location.Kind == LocationKind.None)
                 ? GeneratedLocation.Create(this)
@@ -100,13 +100,13 @@ namespace Semmle.Extraction.CSharp
         /// <param name="cx">Extractor context.</param>
         /// <param name="entity">Program entity.</param>
         /// <param name="l">Location of the entity.</param>
-        public void BindComments(Entity entity, Microsoft.CodeAnalysis.Location l)
+        public void BindComments(Entity entity, Microsoft.CodeAnalysis.Location? l)
         {
             var duplicationGuardKey = GetCurrentTagStackKey();
             CommentGenerator.AddElement(entity.Label, duplicationGuardKey, l);
         }
 
-        protected override bool IsEntityDuplicationGuarded(IEntity entity, [NotNullWhen(true)] out Extraction.Entities.Location loc)
+        protected override bool IsEntityDuplicationGuarded(IEntity entity, [NotNullWhen(true)] out Extraction.Entities.Location? loc)
         {
             if (CreateLocation(entity.ReportingLocation) is Entities.NonGeneratedSourceLocation l)
             {

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Extractor.cs

@@ -71,13 +71,13 @@ namespace Semmle.Extraction.CSharp
 
             Entities.Compilation.Settings = (Directory.GetCurrentDirectory(), args);
 
-            var commandLineArguments = Options.CreateWithEnvironment(Entities.Compilation.Settings.Args);
-            var fileLogger = new FileLogger(commandLineArguments.Verbosity, GetCSharpLogPath());
-            using var logger = commandLineArguments.Console
-                ? new CombinedLogger(new ConsoleLogger(commandLineArguments.Verbosity), fileLogger)
+            var options = Options.CreateWithEnvironment(Entities.Compilation.Settings.Args);
+            var fileLogger = new FileLogger(options.Verbosity, GetCSharpLogPath());
+            using var logger = options.Console
+                ? new CombinedLogger(new ConsoleLogger(options.Verbosity), fileLogger)
                 : (ILogger)fileLogger;
 
-            if (Environment.GetEnvironmentVariable("SEMMLE_CLRTRACER") == "1" && !commandLineArguments.ClrTracer)
+            if (Environment.GetEnvironmentVariable("SEMMLE_CLRTRACER") == "1" && !options.ClrTracer)
             {
                 logger.Log(Severity.Info, "Skipping extraction since already extracted from the CLR tracer");
                 return ExitCode.Ok;
@@ -86,11 +86,11 @@ namespace Semmle.Extraction.CSharp
             var canonicalPathCache = CanonicalPathCache.Create(logger, 1000);
             var pathTransformer = new PathTransformer(canonicalPathCache);
 
-            using var analyser = new Analyser(new LogProgressMonitor(logger), logger, commandLineArguments.AssemblySensitiveTrap, pathTransformer);
-            using var references = new BlockingCollection<MetadataReference>();
+            using var analyser = new TracingAnalyser(new LogProgressMonitor(logger), logger, options.AssemblySensitiveTrap, pathTransformer);
+
             try
             {
-                var compilerVersion = new CompilerVersion(commandLineArguments);
+                var compilerVersion = new CompilerVersion(options);
 
                 if (compilerVersion.SkipExtraction)
                 {
@@ -120,80 +120,7 @@ namespace Semmle.Extraction.CSharp
                     return ExitCode.Ok;
                 }
 
-                var referenceTasks = ResolveReferences(compilerArguments, analyser, canonicalPathCache, references);
-
-                var syntaxTrees = new List<SyntaxTree>();
-                var syntaxTreeTasks = ReadSyntaxTrees(
-                    compilerArguments.SourceFiles.
-                    Select(src => canonicalPathCache.GetCanonicalPath(src.Path)),
-                    analyser,
-                    compilerArguments.ParseOptions,
-                    compilerArguments.Encoding,
-                    syntaxTrees);
-
-                var sw1 = new Stopwatch();
-                sw1.Start();
-
-                Parallel.Invoke(
-                    new ParallelOptions { MaxDegreeOfParallelism = commandLineArguments.Threads },
-                    referenceTasks.Interleave(syntaxTreeTasks).ToArray());
-
-                if (syntaxTrees.Count == 0)
-                {
-                    logger.Log(Severity.Error, "  No source files");
-                    ++analyser.CompilationErrors;
-                    return ExitCode.Failed;
-                }
-
-                // csc.exe (CSharpCompiler.cs) also provides CompilationOptions
-                // .WithMetadataReferenceResolver(),
-                // .WithXmlReferenceResolver() and
-                // .WithSourceReferenceResolver().
-                // These would be needed if we hadn't explicitly provided the source/references
-                // already.
-                var compilation = CSharpCompilation.Create(
-                    compilerArguments.CompilationName,
-                    syntaxTrees,
-                    references,
-                    compilerArguments.CompilationOptions.
-                        WithAssemblyIdentityComparer(DesktopAssemblyIdentityComparer.Default).
-                        WithStrongNameProvider(new DesktopStrongNameProvider(compilerArguments.KeyFileSearchPaths))
-                    );
-
-                analyser.EndInitialize(compilerArguments, commandLineArguments, compilation);
-                analyser.AnalyseCompilation();
-                analyser.AnalyseReferences();
-
-                foreach (var tree in compilation.SyntaxTrees)
-                {
-                    analyser.AnalyseTree(tree);
-                }
-
-                var currentProcess = Process.GetCurrentProcess();
-                var cpuTime1 = currentProcess.TotalProcessorTime;
-                var userTime1 = currentProcess.UserProcessorTime;
-                sw1.Stop();
-                logger.Log(Severity.Info, "  Models constructed in {0}", sw1.Elapsed);
-
-                var sw2 = new Stopwatch();
-                sw2.Start();
-                analyser.PerformExtraction(commandLineArguments.Threads);
-                sw2.Stop();
-                var cpuTime2 = currentProcess.TotalProcessorTime;
-                var userTime2 = currentProcess.UserProcessorTime;
-
-                var performance = new Entities.PerformanceMetrics()
-                {
-                    Frontend = new Entities.Timings() { Elapsed = sw1.Elapsed, Cpu = cpuTime1, User = userTime1 },
-                    Extractor = new Entities.Timings() { Elapsed = sw2.Elapsed, Cpu = cpuTime2 - cpuTime1, User = userTime2 - userTime1 },
-                    Total = new Entities.Timings() { Elapsed = stopwatch.Elapsed, Cpu = cpuTime2, User = userTime2 },
-                    PeakWorkingSet = currentProcess.PeakWorkingSet64
-                };
-
-                analyser.LogPerformance(performance);
-                logger.Log(Severity.Info, "  Extraction took {0}", sw2.Elapsed);
-
-                return analyser.TotalErrors == 0 ? ExitCode.Ok : ExitCode.Errors;
+                return AnalyseTracing(analyser, compilerArguments, options, canonicalPathCache, stopwatch);
             }
             catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
             {
@@ -216,7 +143,10 @@ namespace Semmle.Extraction.CSharp
             // 3) Directories specified by / lib.
             // 4) Directories specified by the LIB environment variable.
 
-            yield return args.BaseDirectory;
+            if (args.BaseDirectory is object)
+            {
+                yield return args.BaseDirectory;
+            }
 
             foreach (var r in args.ReferencePaths)
                 yield return r;
@@ -289,7 +219,7 @@ namespace Semmle.Extraction.CSharp
         /// The constructed syntax trees will be added (thread-safely) to the supplied
         /// list <paramref name="ret"/>.
         /// </summary>
-        private static IEnumerable<Action> ReadSyntaxTrees(IEnumerable<string> sources, Analyser analyser, CSharpParseOptions parseOptions, Encoding encoding, IList<SyntaxTree> ret)
+        private static IEnumerable<Action> ReadSyntaxTrees(IEnumerable<string> sources, Analyser analyser, CSharpParseOptions? parseOptions, Encoding? encoding, IList<SyntaxTree> ret)
         {
             return sources.Select<string, Action>(path => () =>
             {
@@ -318,68 +248,16 @@ namespace Semmle.Extraction.CSharp
             ILogger logger,
             CommonOptions options)
         {
+            var stopwatch = new Stopwatch();
+            stopwatch.Start();
+
             var canonicalPathCache = CanonicalPathCache.Create(logger, 1000);
             var pathTransformer = new PathTransformer(canonicalPathCache);
 
-            using var analyser = new Analyser(pm, logger, false, pathTransformer);
-            using var references = new BlockingCollection<MetadataReference>();
+            using var analyser = new StandaloneAnalyser(pm, logger, false, pathTransformer);
             try
             {
-                var referenceTasks = referencePaths.Select<string, Action>(path => () =>
-                {
-                    var reference = MetadataReference.CreateFromFile(path);
-                    references.Add(reference);
-                });
-
-                var syntaxTrees = new List<SyntaxTree>();
-                var syntaxTreeTasks = ReadSyntaxTrees(sources, analyser, null, null, syntaxTrees);
-
-                var sw = new Stopwatch();
-                sw.Start();
-
-                Parallel.Invoke(
-                    new ParallelOptions { MaxDegreeOfParallelism = options.Threads },
-                    referenceTasks.Interleave(syntaxTreeTasks).ToArray());
-
-                if (syntaxTrees.Count == 0)
-                {
-                    analyser.Logger.Log(Severity.Error, "  No source files");
-                    ++analyser.CompilationErrors;
-                }
-
-                var compilation = CSharpCompilation.Create(
-                    "csharp.dll",
-                    syntaxTrees,
-                    references
-                    );
-
-                analyser.InitializeStandalone(compilation, options);
-                analyser.AnalyseReferences();
-
-                foreach (var tree in compilation.SyntaxTrees)
-                {
-                    analyser.AnalyseTree(tree);
-                }
-
-                sw.Stop();
-                analyser.Logger.Log(Severity.Info, "  Models constructed in {0}", sw.Elapsed);
-
-                sw.Restart();
-                analyser.PerformExtraction(options.Threads);
-                sw.Stop();
-                analyser.Logger.Log(Severity.Info, "  Extraction took {0}", sw.Elapsed);
-
-                foreach (var type in analyser.MissingNamespaces)
-                {
-                    pm.MissingNamespace(type);
-                }
-
-                foreach (var type in analyser.MissingTypes)
-                {
-                    pm.MissingType(type);
-                }
-
-                pm.MissingSummary(analyser.MissingTypes.Count(), analyser.MissingNamespaces.Count());
+                AnalyseStandalone(analyser, sources, referencePaths, options, pm, stopwatch);
             }
             catch (Exception ex)  // lgtm[cs/catch-of-all-exceptions]
             {
@@ -387,6 +265,160 @@ namespace Semmle.Extraction.CSharp
             }
         }
 
+        private static ExitCode Analyse(Stopwatch stopwatch, Analyser analyser, CommonOptions options,
+            Func<BlockingCollection<MetadataReference>, IEnumerable<Action>> getResolvedReferenceTasks,
+            Func<Analyser, List<SyntaxTree>, IEnumerable<Action>> getSyntaxTreeTasks,
+            Func<IEnumerable<SyntaxTree>, IEnumerable<MetadataReference>, CSharpCompilation> getCompilation,
+            Action<CSharpCompilation, CommonOptions> initializeAnalyser,
+            Action analyseCompilation,
+            Action<Entities.PerformanceMetrics> logPerformance,
+            Action postProcess)
+        {
+            using var references = new BlockingCollection<MetadataReference>();
+            var referenceTasks = getResolvedReferenceTasks(references);
+
+            var syntaxTrees = new List<SyntaxTree>();
+            var syntaxTreeTasks = getSyntaxTreeTasks(analyser, syntaxTrees);
+
+            var sw = new Stopwatch();
+            sw.Start();
+
+            Parallel.Invoke(
+                new ParallelOptions { MaxDegreeOfParallelism = options.Threads },
+                referenceTasks.Interleave(syntaxTreeTasks).ToArray());
+
+            if (syntaxTrees.Count == 0)
+            {
+                analyser.Logger.Log(Severity.Error, "  No source files");
+                ++analyser.CompilationErrors;
+                if (analyser is TracingAnalyser)
+                {
+                    return ExitCode.Failed;
+                }
+            }
+
+            var compilation = getCompilation(syntaxTrees, references);
+
+            initializeAnalyser(compilation, options);
+            analyseCompilation();
+            analyser.AnalyseReferences();
+
+            foreach (var tree in compilation.SyntaxTrees)
+            {
+                analyser.AnalyseTree(tree);
+            }
+
+            sw.Stop();
+            analyser.Logger.Log(Severity.Info, "  Models constructed in {0}", sw.Elapsed);
+            var elapsed = sw.Elapsed;
+
+            var currentProcess = Process.GetCurrentProcess();
+            var cpuTime1 = currentProcess.TotalProcessorTime;
+            var userTime1 = currentProcess.UserProcessorTime;
+
+            sw.Restart();
+            analyser.PerformExtraction(options.Threads);
+            sw.Stop();
+            var cpuTime2 = currentProcess.TotalProcessorTime;
+            var userTime2 = currentProcess.UserProcessorTime;
+
+            var performance = new Entities.PerformanceMetrics()
+            {
+                Frontend = new Entities.Timings() { Elapsed = elapsed, Cpu = cpuTime1, User = userTime1 },
+                Extractor = new Entities.Timings() { Elapsed = sw.Elapsed, Cpu = cpuTime2 - cpuTime1, User = userTime2 - userTime1 },
+                Total = new Entities.Timings() { Elapsed = stopwatch.Elapsed, Cpu = cpuTime2, User = userTime2 },
+                PeakWorkingSet = currentProcess.PeakWorkingSet64
+            };
+
+            logPerformance(performance);
+            analyser.Logger.Log(Severity.Info, "  Extraction took {0}", sw.Elapsed);
+
+            postProcess();
+
+            return analyser.TotalErrors == 0 ? ExitCode.Ok : ExitCode.Errors;
+        }
+
+        private static void AnalyseStandalone(
+            StandaloneAnalyser analyser,
+            IEnumerable<string> sources,
+            IEnumerable<string> referencePaths,
+            CommonOptions options,
+            IProgressMonitor progressMonitor,
+            Stopwatch stopwatch)
+        {
+            Analyse(stopwatch, analyser, options,
+                references => GetResolvedReferencesStandalone(referencePaths, references),
+                (analyser, syntaxTrees) => ReadSyntaxTrees(sources, analyser, null, null, syntaxTrees),
+                (syntaxTrees, references) => CSharpCompilation.Create("csharp.dll", syntaxTrees, references),
+                (compilation, options) => analyser.InitializeStandalone(compilation, options),
+                () => { },
+                _ => { },
+                () =>
+                {
+                    foreach (var type in analyser.MissingNamespaces)
+                    {
+                        progressMonitor.MissingNamespace(type);
+                    }
+
+                    foreach (var type in analyser.MissingTypes)
+                    {
+                        progressMonitor.MissingType(type);
+                    }
+
+                    progressMonitor.MissingSummary(analyser.MissingTypes.Count(), analyser.MissingNamespaces.Count());
+                });
+        }
+
+        private static ExitCode AnalyseTracing(
+            TracingAnalyser analyser,
+            CSharpCommandLineArguments compilerArguments,
+            Options options,
+            CanonicalPathCache canonicalPathCache,
+            Stopwatch stopwatch)
+        {
+            return Analyse(stopwatch, analyser, options,
+                references => ResolveReferences(compilerArguments, analyser, canonicalPathCache, references),
+                (analyser, syntaxTrees) =>
+                {
+                    return ReadSyntaxTrees(
+                        compilerArguments.SourceFiles.Select(src => canonicalPathCache.GetCanonicalPath(src.Path)),
+                        analyser,
+                        compilerArguments.ParseOptions,
+                        compilerArguments.Encoding,
+                        syntaxTrees);
+                },
+                (syntaxTrees, references) =>
+                {
+                    // csc.exe (CSharpCompiler.cs) also provides CompilationOptions
+                    // .WithMetadataReferenceResolver(),
+                    // .WithXmlReferenceResolver() and
+                    // .WithSourceReferenceResolver().
+                    // These would be needed if we hadn't explicitly provided the source/references
+                    // already.
+                    return CSharpCompilation.Create(
+                        compilerArguments.CompilationName,
+                        syntaxTrees,
+                        references,
+                        compilerArguments.CompilationOptions.
+                            WithAssemblyIdentityComparer(DesktopAssemblyIdentityComparer.Default).
+                            WithStrongNameProvider(new DesktopStrongNameProvider(compilerArguments.KeyFileSearchPaths))
+                        );
+                },
+                (compilation, options) => analyser.EndInitialize(compilerArguments, options, compilation),
+                () => analyser.AnalyseCompilation(),
+                performance => analyser.LogPerformance(performance),
+                () => { });
+        }
+
+        private static IEnumerable<Action> GetResolvedReferencesStandalone(IEnumerable<string> referencePaths, BlockingCollection<MetadataReference> references)
+        {
+            return referencePaths.Select<string, Action>(path => () =>
+            {
+                var reference = MetadataReference.CreateFromFile(path);
+                references.Add(reference);
+            });
+        }
+
         /// <summary>
         /// Gets the path to the `csharp.log` file written to by the C# extractor.
         /// </summary>