Multi-targeting net5.0; fixed nullable warnings.

bench/Autofac.Benchmarks/Autofac.Benchmarks.csproj

@@ -29,7 +29,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.6.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.2">
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "3.1.302",
+    "version": "5.0.100-rc.2.20479.15",
     "rollForward": "latestFeature"
   }
 }

src/Autofac/Autofac.csproj

@@ -4,7 +4,7 @@
     <Description>Autofac is an IoC container for Microsoft .NET. It manages the dependencies between classes so that applications stay easy to change as they grow in size and complexity.</Description>
     <!-- VersionPrefix patched by AppVeyor -->
     <VersionPrefix>0.0.1</VersionPrefix>
-    <TargetFrameworks>netstandard2.1;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.1;netstandard2.0;net5.0</TargetFrameworks>
     <LangVersion>latest</LangVersion>
     <Nullable>enable</Nullable>
     <NoWarn>$(NoWarn);CS1591;IDE0008</NoWarn>

src/Autofac/Builder/IHideObjectMembers.cs

@@ -36,7 +36,7 @@ public interface IHideObjectMembers
         /// </summary>
         /// <returns>Standard result.</returns>
         [EditorBrowsable(EditorBrowsableState.Never)]
-        string ToString();
+        string? ToString();
 
         /// <summary>
         /// Standard System.Object member.

src/Autofac/Core/Activators/Reflection/AutowiringPropertyInjector.cs

@@ -72,7 +72,8 @@ public static void InjectProperties(IComponentContext context, object instance,
                     continue;
                 }
 
-                var setParameter = property.SetMethod.GetParameters()[0];
+                // SetMethod will be non-null if GetInjectableProperties included it.
+                var setParameter = property.SetMethod!.GetParameters()[0];
                 var valueProvider = (Func<object?>?)null;
                 var parameter = resolveParameters.FirstOrDefault(p => p.CanSupplyValue(setParameter, context, out valueProvider));
                 if (parameter != null)
@@ -103,7 +104,7 @@ private static IEnumerable<PropertyInfo> GetInjectableProperties(Type instanceTy
 
                 // SetMethod will be non-null if CanWrite is true.
                 // Don't want to inject onto static properties.
-                if (property.SetMethod.IsStatic)
+                if (property.SetMethod!.IsStatic)
                 {
                     continue;
                 }
@@ -115,7 +116,8 @@ private static IEnumerable<PropertyInfo> GetInjectableProperties(Type instanceTy
                     continue;
                 }
 
-                if (propertyType.IsArray && propertyType.GetElementType().IsValueType)
+                // GetElementType will be non-null if IsArray is true.
+                if (propertyType.IsArray && propertyType.GetElementType()!.IsValueType)
                 {
                     continue;
                 }
@@ -136,8 +138,11 @@ private static IEnumerable<PropertyInfo> GetInjectableProperties(Type instanceTy
 
         private static Action<object, object?> MakeFastPropertySetter(PropertyInfo propertyInfo)
         {
-            var setMethod = propertyInfo.SetMethod;
-            var typeInput = setMethod.DeclaringType;
+            // SetMethod will be non-null if we're trying to make a setter for it.
+            var setMethod = propertyInfo.SetMethod!;
+
+            // DeclaringType will always be set for properties.
+            var typeInput = setMethod.DeclaringType!;
             var parameters = setMethod.GetParameters();
             var parameterType = parameters[0].ParameterType;
 

src/Autofac/Core/Activators/Reflection/BoundConstructor.cs

@@ -112,11 +112,11 @@ public object Instantiate()
             }
             catch (TargetInvocationException ex)
             {
-                throw new DependencyResolutionException(string.Format(CultureInfo.CurrentCulture, BoundConstructorResources.ExceptionDuringInstantiation, TargetConstructor, TargetConstructor.DeclaringType.Name), ex.InnerException);
+                throw new DependencyResolutionException(string.Format(CultureInfo.CurrentCulture, BoundConstructorResources.ExceptionDuringInstantiation, TargetConstructor, TargetConstructor.DeclaringType!.Name), ex.InnerException);
             }
             catch (Exception ex)
             {
-                throw new DependencyResolutionException(string.Format(CultureInfo.CurrentCulture, BoundConstructorResources.ExceptionDuringInstantiation, TargetConstructor, TargetConstructor.DeclaringType.Name), ex);
+                throw new DependencyResolutionException(string.Format(CultureInfo.CurrentCulture, BoundConstructorResources.ExceptionDuringInstantiation, TargetConstructor, TargetConstructor.DeclaringType!.Name), ex);
             }
         }
 

src/Autofac/Core/Activators/Reflection/ConstructorBinder.cs

@@ -154,7 +154,9 @@ public BoundConstructor Bind(IEnumerable<Parameter> availableParameters, ICompon
         private static MethodCallExpression ConvertPrimitiveType(Expression valueExpression, Type conversionType)
         {
             var changeTypeMethod = typeof(Convert).GetRuntimeMethod(nameof(Convert.ChangeType), new[] { typeof(object), typeof(Type) });
-            return Expression.Call(changeTypeMethod, valueExpression, Expression.Constant(conversionType));
+
+            // changeTypeMethod will always be non-null; Convert.ChangeType definitely exists.
+            return Expression.Call(changeTypeMethod!, valueExpression, Expression.Constant(conversionType));
         }
 
         private static ParameterInfo? DetectIllegalParameter(ParameterInfo[] constructorArgs)

src/Autofac/Core/Activators/Reflection/MatchingSignatureConstructorSelector.cs

@@ -69,7 +69,8 @@ public BoundConstructor SelectConstructorBinding(BoundConstructor[] constructorB
                 throw new ArgumentException(MatchingSignatureConstructorSelectorResources.AtLeastOneBindingRequired);
             }
 
-            var targetTypeName = constructorBindings[0].TargetConstructor.DeclaringType.Name;
+            // DeclaringType will be non-null for constructors.
+            var targetTypeName = constructorBindings[0].TargetConstructor.DeclaringType!.Name;
             var signature = string.Join(", ", _signature.Select(t => t.Name).ToArray());
 
             if (matchingCount == 0)

src/Autofac/Core/AutoActivateService.cs

@@ -32,7 +32,7 @@ internal class AutoActivateService : Service
         /// All services of this type are considered "equal".
         /// </para>
         /// </remarks>
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             var that = obj as AutoActivateService;
             return that != null;

src/Autofac/Core/Container.cs

@@ -172,7 +172,8 @@ protected override async ValueTask DisposeAsync(bool disposing)
         /// </returns>
         public object GetService(Type serviceType)
         {
-            return ((IServiceProvider)_rootLifetimeScope).GetService(serviceType);
+            // GetService implementation on LifetimeScope either returns an object, or throws.
+            return ((IServiceProvider)_rootLifetimeScope).GetService(serviceType)!;
         }
     }
 }

src/Autofac/Core/DependencyResolutionException.cs

@@ -39,7 +39,7 @@ public DependencyResolutionException(string message)
         /// </summary>
         /// <param name="message">The message.</param>
         /// <param name="innerException">The inner exception.</param>
-        public DependencyResolutionException(string message, Exception innerException)
+        public DependencyResolutionException(string message, Exception? innerException)
             : base(message, innerException)
         {
         }

src/Autofac/Core/ISharingLifetimeScope.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Autofac.Core
 {
@@ -26,7 +27,7 @@ public interface ISharingLifetimeScope : ILifetimeScope
         /// <param name="id">Key to look up.</param>
         /// <param name="value">The instance that has the specified key.</param>
         /// <returns><c>true</c> if the key was found; otherwise, <c>false</c>.</returns>
-        bool TryGetSharedInstance(Guid id, out object value);
+        bool TryGetSharedInstance(Guid id, [NotNullWhen(true)] out object? value);
 
         /// <summary>
         /// Try to retrieve a shared instance based on a primary GUID key and
@@ -39,7 +40,7 @@ public interface ISharingLifetimeScope : ILifetimeScope
         /// </param>
         /// <param name="value">The instance that has the specified keys.</param>
         /// <returns><c>true</c> if the key was found; otherwise, <c>false</c>.</returns>
-        bool TryGetSharedInstance(Guid primaryId, Guid? qualifyingId, out object value);
+        bool TryGetSharedInstance(Guid primaryId, Guid? qualifyingId, [NotNullWhen(true)] out object? value);
 
         /// <summary>
         /// Creates a shared instance with a GUID key.

src/Autofac/Core/Lifetime/LifetimeScope.cs

@@ -363,10 +363,10 @@ public object CreateSharedInstance(Guid primaryId, Guid? qualifyingId, Func<obje
         }
 
         /// <inheritdoc />
-        public bool TryGetSharedInstance(Guid id, out object value) => _sharedInstances.TryGetValue(id, out value);
+        public bool TryGetSharedInstance(Guid id, [NotNullWhen(true)] out object? value) => _sharedInstances.TryGetValue(id, out value);
 
         /// <inheritdoc/>
-        public bool TryGetSharedInstance(Guid primaryId, Guid? qualifyingId, out object value)
+        public bool TryGetSharedInstance(Guid primaryId, Guid? qualifyingId, [NotNullWhen(true)] out object? value)
         {
             return qualifyingId == null
                 ? TryGetSharedInstance(primaryId, out value)

src/Autofac/Core/Registration/ComponentRegistryBuilder.cs

@@ -34,14 +34,14 @@ internal ComponentRegistryBuilder(IRegisteredServicesTracker registeredServicesT
             _registeredServicesTracker.RegistrationSourceAdded += OnRegistrationSourceAdded;
         }
 
-        private void OnRegistered(object sender, IComponentRegistration e)
+        private void OnRegistered(object? sender, IComponentRegistration e)
         {
             var handler = GetRegistered();
 
             handler?.Invoke(this, new ComponentRegisteredEventArgs(this, e));
         }
 
-        private void OnRegistrationSourceAdded(object sender, IRegistrationSource e)
+        private void OnRegistrationSourceAdded(object? sender, IRegistrationSource e)
         {
             var handler = GetRegistrationSourceAdded();
 

src/Autofac/Core/Registration/ServiceRegistrationInfo.cs

@@ -301,7 +301,8 @@ public void SkipSource(IRegistrationSource source)
         {
             EnforceDuringInitialization();
 
-            _sourcesToQuery = new Queue<IRegistrationSource>(_sourcesToQuery.Where(rs => rs != source));
+            // _sourcesToQuery always non-null during Initialization.
+            _sourcesToQuery = new Queue<IRegistrationSource>(_sourcesToQuery!.Where(rs => rs != source));
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]

src/Autofac/Core/Service.cs

@@ -59,7 +59,7 @@ public override string ToString()
         /// </returns>
         /// <exception cref="System.NullReferenceException">The <paramref name="obj"/> parameter is null.</exception>
         [SuppressMessage("Microsoft.Design", "CA1065:DoNotRaiseExceptionsInUnexpectedLocations", Justification = "This is an attempt to make Equals 'abstract' when it normally isn't.")]
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             throw new NotImplementedException(ServiceResources.MustOverrideEquals);
         }

src/Autofac/Core/TypedService.cs

@@ -29,7 +29,7 @@ public TypedService(Type serviceType)
         /// Gets a human-readable description of the service.
         /// </summary>
         /// <value>The description.</value>
-        public override string Description => ServiceType.FullName;
+        public override string Description => ServiceType.FullName!;
 
         /// <summary>
         /// Indicates whether the current object is equal to another object of the same type.
@@ -56,7 +56,7 @@ public bool Equals(TypedService? other)
         /// true if the specified <see cref="object"/> is equal to the current <see cref="object"/>; otherwise, false.
         /// </returns>
         /// <exception cref="NullReferenceException">The <paramref name="obj"/> parameter is null.</exception>
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return Equals(obj as TypedService);
         }

src/Autofac/Core/UniqueService.cs

@@ -42,7 +42,7 @@ public UniqueService(Guid id)
         /// true if the specified <see cref="object"/> is equal to the current <see cref="object"/>; otherwise, false.
         /// </returns>
         /// <exception cref="System.NullReferenceException">The <paramref name="obj"/> parameter is null.</exception>
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             var that = obj as UniqueService;
 

src/Autofac/Diagnostics/DiagnosticTracerBase.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Autofac Project. All rights reserved.
+// Copyright (c) Autofac Project. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
 using System;
@@ -52,7 +52,7 @@ namespace Autofac.Diagnostics
     /// </para>
     /// </remarks>
     /// <seealso cref="DefaultDiagnosticTracer"/>
-    public abstract class DiagnosticTracerBase : IObserver<KeyValuePair<string, object>>
+    public abstract class DiagnosticTracerBase : IObserver<KeyValuePair<string, object?>>
     {
         /// <summary>
         /// The list of event names to which this observer is subscribed.
@@ -207,7 +207,7 @@ public bool IsEnabled(string diagnosticName)
         /// <summary>
         /// Notifies the observer that the provider has finished sending push-based notifications.
         /// </summary>
-        void IObserver<KeyValuePair<string, object>>.OnCompleted()
+        void IObserver<KeyValuePair<string, object?>>.OnCompleted()
         {
             // If there was something to dispose or clean up, here's where it would
             // happen, but we don't have anything like that.
@@ -219,7 +219,7 @@ void IObserver<KeyValuePair<string, object>>.OnCompleted()
         /// <param name="error">
         /// An object that provides additional information about the error.
         /// </param>
-        void IObserver<KeyValuePair<string, object>>.OnError(Exception error)
+        void IObserver<KeyValuePair<string, object?>>.OnError(Exception error)
         {
             // The internal diagnostic source isn't really going to experience an
             // error condition (which is not the same as _reporting errors_) so
@@ -232,7 +232,7 @@ void IObserver<KeyValuePair<string, object>>.OnError(Exception error)
         /// <param name="value">
         /// The current notification information.
         /// </param>
-        void IObserver<KeyValuePair<string, object>>.OnNext(KeyValuePair<string, object> value)
+        void IObserver<KeyValuePair<string, object?>>.OnNext(KeyValuePair<string, object?> value)
         {
             // This is what gets called when a new diagnostic event occurs.
             Write(value.Key, value.Value);
@@ -400,7 +400,7 @@ protected virtual void OnRequestSuccess(RequestDiagnosticData data)
         /// options.
         /// </para>
         /// </remarks>
-        protected virtual void Write(string diagnosticName, object data)
+        protected virtual void Write(string diagnosticName, object? data)
         {
             if (data == null || !IsEnabled(diagnosticName))
             {

src/Autofac/Features/AttributeFilters/MetadataFilterAttribute.cs

@@ -128,7 +128,7 @@ public MetadataFilterAttribute(string key, object value)
         /// <exception cref="System.ArgumentNullException">
         /// Thrown if <paramref name="parameter" /> or <paramref name="context" /> is <see langword="null" />.
         /// </exception>
-        public override object ResolveParameter(ParameterInfo parameter, IComponentContext context)
+        public override object? ResolveParameter(ParameterInfo parameter, IComponentContext context)
         {
             if (parameter == null)
             {
@@ -176,15 +176,16 @@ public override bool CanResolveParameter(ParameterInfo parameter, IComponentCont
             // this is the place to do it.
             var elementType = GetElementType(parameter.ParameterType);
 
-            return (bool)CanResolveMethod.MakeGenericMethod(elementType).Invoke(null, new[] { context, Key, Value });
+            // CanResolveMethod always returns a value.
+            return (bool)CanResolveMethod.MakeGenericMethod(elementType).Invoke(null, new[] { context, Key, Value })!;
         }
 
         private static Type GetElementType(Type type)
         {
             return type.IsGenericEnumerableInterfaceType() ? type.GenericTypeArguments[0] : type;
         }
 
-        private static T FilterOne<T>(IComponentContext context, string metadataKey, object metadataValue)
+        private static T? FilterOne<T>(IComponentContext context, string metadataKey, object metadataValue)
         {
             // Using Lazy<T> to ensure components that aren't actually used won't get activated.
             return context.Resolve<IEnumerable<Meta<Lazy<T>>>>()

src/Autofac/Features/Collections/CollectionRegistrationSource.cs

@@ -87,7 +87,8 @@ public IEnumerable<IComponentRegistration> RegistrationsFor(Service service, Fun
             }
             else if (serviceType.IsArray)
             {
-                elementType = serviceType.GetElementType();
+                // GetElementType always non-null if IsArray is true.
+                elementType = serviceType.GetElementType()!;
                 limitType = serviceType;
                 factory = GenerateArrayFactory(elementType);
             }
@@ -160,7 +161,9 @@ private static Func<int, IList> GenerateListFactory(Type elementType)
             var parameter = Expression.Parameter(typeof(int));
             var genericType = typeof(List<>).MakeGenericType(elementType);
             var constructor = genericType.GetMatchingConstructor(new[] { typeof(int) });
-            var newList = Expression.New(constructor, parameter);
+
+            // We know that List<> has the constructor we need.
+            var newList = Expression.New(constructor!, parameter);
             return Expression.Lambda<Func<int, IList>>(newList, parameter).Compile();
         }
 

src/Autofac/Features/Decorators/DecoratorService.cs

@@ -48,7 +48,7 @@ public Service ChangeType(Type newType)
         }
 
         /// <inheritdoc />
-        public bool Equals(DecoratorService other)
+        public bool Equals(DecoratorService? other)
         {
             if (other is null)
             {
@@ -64,7 +64,7 @@ public bool Equals(DecoratorService other)
         }
 
         /// <inheritdoc />
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (obj is null)
             {