Use T? for unconstrained nullable types (#25772)

src/Http/Authentication.Abstractions/src/AuthenticationProperties.cs

@@ -144,8 +144,7 @@ namespace Microsoft.AspNetCore.Authentication
         /// <typeparam name="T">Parameter type.</typeparam>
         /// <param name="key">Parameter key.</param>
         /// <returns>Retrieved value or the default value if the property is not set.</returns>
-        [return: MaybeNull]
+        public T? GetParameter<T>(string key)
-        public T GetParameter<T>(string key)
             => Parameters.TryGetValue(key, out var obj) && obj is T value ? value : default;
 
         /// <summary>
@@ -154,7 +153,7 @@ namespace Microsoft.AspNetCore.Authentication
         /// <typeparam name="T">Parameter type.</typeparam>
         /// <param name="key">Parameter key.</param>
         /// <param name="value">Value to set.</param>
-        public void SetParameter<T>(string key, [MaybeNull] T value)
+        public void SetParameter<T>(string key, T value)
             => Parameters[key] = value;
 
         /// <summary>

src/Http/Headers/src/BaseHeaderParser.cs

@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Diagnostics.CodeAnalysis;
 using Microsoft.Extensions.Primitives;
 
 namespace Microsoft.Net.Http.Headers
@@ -13,9 +12,9 @@ namespace Microsoft.Net.Http.Headers
         {
         }
 
-        protected abstract int GetParsedValueLength(StringSegment value, int startIndex, [MaybeNull] out T parsedValue);
+        protected abstract int GetParsedValueLength(StringSegment value, int startIndex, out T? parsedValue);
 
-        public sealed override bool TryParseValue(StringSegment value, ref int index, [MaybeNull] out T parsedValue)
+        public sealed override bool TryParseValue(StringSegment value, ref int index, out T? parsedValue)
         {
             parsedValue = default;
 

src/Http/Headers/src/CacheControlHeaderValue.cs

@@ -32,7 +32,7 @@ namespace Microsoft.Net.Http.Headers
         // Cache-Control headers, only one instance of CacheControlHeaderValue is created (if all headers contain valid
         // values, otherwise we may have multiple strings containing the invalid values).
         private static readonly HttpHeaderParser<CacheControlHeaderValue> Parser
-            = new GenericHeaderParser<CacheControlHeaderValue>(true, GetCacheControlLength!);
+            = new GenericHeaderParser<CacheControlHeaderValue>(true, GetCacheControlLength);
 
         private static readonly Action<StringSegment> CheckIsValidTokenAction = CheckIsValidToken;
 

src/Http/Headers/src/ContentDispositionHeaderValue.cs

@@ -27,7 +27,7 @@ namespace Microsoft.Net.Http.Headers
         private static readonly char[] SingleQuote = new char[] { '\'' };
 
         private static readonly HttpHeaderParser<ContentDispositionHeaderValue> Parser
-            = new GenericHeaderParser<ContentDispositionHeaderValue>(false, GetDispositionTypeLength!);
+            = new GenericHeaderParser<ContentDispositionHeaderValue>(false, GetDispositionTypeLength);
 
         // Use list instead of dictionary since we may have multiple parameters with the same name.
         private ObjectCollection<NameValueHeaderValue>? _parameters;

src/Http/Headers/src/ContentRangeHeaderValue.cs

@@ -13,7 +13,7 @@ namespace Microsoft.Net.Http.Headers
     public class ContentRangeHeaderValue
     {
         private static readonly HttpHeaderParser<ContentRangeHeaderValue> Parser
-            = new GenericHeaderParser<ContentRangeHeaderValue>(false, GetContentRangeLength!);
+            = new GenericHeaderParser<ContentRangeHeaderValue>(false, GetContentRangeLength);
 
         private StringSegment _unit;
         private long? _from;

src/Http/Headers/src/EntityTagHeaderValue.cs

@@ -14,13 +14,13 @@ namespace Microsoft.Net.Http.Headers
         // Note that the ETag header does not allow a * but we're not that strict: We allow both '*' and ETag values in a single value.
         // We can't guarantee that a single parsed value will be used directly in an ETag header.
         private static readonly HttpHeaderParser<EntityTagHeaderValue> SingleValueParser
-            = new GenericHeaderParser<EntityTagHeaderValue>(false, GetEntityTagLength!);
+            = new GenericHeaderParser<EntityTagHeaderValue>(false, GetEntityTagLength);
         // Note that if multiple ETag values are allowed (e.g. 'If-Match', 'If-None-Match'), according to the RFC
         // the value must either be '*' or a list of ETag values. It's not allowed to have both '*' and a list of
         // ETag values. We're not that strict: We allow both '*' and ETag values in a list. If the server sends such
         // an invalid list, we want to be able to represent it using the corresponding header property.
         private static readonly HttpHeaderParser<EntityTagHeaderValue> MultipleValueParser
-            = new GenericHeaderParser<EntityTagHeaderValue>(true, GetEntityTagLength!);
+            = new GenericHeaderParser<EntityTagHeaderValue>(true, GetEntityTagLength);
 
         private static EntityTagHeaderValue? AnyType;
 

src/Http/Headers/src/GenericHeaderParser.cs

@@ -2,14 +2,13 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Diagnostics.CodeAnalysis;
 using Microsoft.Extensions.Primitives;
 
 namespace Microsoft.Net.Http.Headers
 {
     internal sealed class GenericHeaderParser<T> : BaseHeaderParser<T>
     {
-        internal delegate int GetParsedValueLengthDelegate(StringSegment value, int startIndex, [MaybeNull] out T parsedValue);
+        internal delegate int GetParsedValueLengthDelegate(StringSegment value, int startIndex, out T? parsedValue);
 
         private GetParsedValueLengthDelegate _getParsedValueLength;
 
@@ -24,7 +23,7 @@ namespace Microsoft.Net.Http.Headers
             _getParsedValueLength = getParsedValueLength;
         }
 
-        protected override int GetParsedValueLength(StringSegment value, int startIndex, [MaybeNull] out T parsedValue)
+        protected override int GetParsedValueLength(StringSegment value, int startIndex, out T? parsedValue)
         {
             return _getParsedValueLength(value, startIndex, out parsedValue);
         }

src/Http/Headers/src/HttpHeaderParser.cs

@@ -28,10 +28,9 @@ namespace Microsoft.Net.Http.Headers
         // pointing to the next non-whitespace character after a delimiter. E.g. if called with a start index of 0
         // for string "value , second_value", then after the call completes, 'index' must point to 's', i.e. the first
         // non-whitespace after the separator ','.
-        public abstract bool TryParseValue(StringSegment value, ref int index, [MaybeNull] out T parsedValue);
+        public abstract bool TryParseValue(StringSegment value, ref int index, out T? parsedValue);
 
-        [return: MaybeNull]
+        public T? ParseValue(StringSegment value, ref int index)
-        public T ParseValue(StringSegment value, ref int index)
         {
             // Index may be value.Length (e.g. both 0). This may be allowed for some headers (e.g. Accept but not
             // allowed by others (e.g. Content-Length). The parser has to decide if this is valid or not.

src/Http/Headers/src/MediaTypeHeaderValue.cs

@@ -30,9 +30,9 @@ namespace Microsoft.Net.Http.Headers
         private static readonly char[] PeriodCharacterArray = new char[] { PeriodCharacter };
 
         private static readonly HttpHeaderParser<MediaTypeHeaderValue> SingleValueParser
-            = new GenericHeaderParser<MediaTypeHeaderValue>(false, GetMediaTypeLength!);
+            = new GenericHeaderParser<MediaTypeHeaderValue>(false, GetMediaTypeLength);
         private static readonly HttpHeaderParser<MediaTypeHeaderValue> MultipleValueParser
-            = new GenericHeaderParser<MediaTypeHeaderValue>(true, GetMediaTypeLength!);
+            = new GenericHeaderParser<MediaTypeHeaderValue>(true, GetMediaTypeLength);
 
         // Use a collection instead of a dictionary since we may have multiple parameters with the same name.
         private ObjectCollection<NameValueHeaderValue>? _parameters;

src/Http/Headers/src/NameValueHeaderValue.cs

@@ -17,9 +17,9 @@ namespace Microsoft.Net.Http.Headers
     public class NameValueHeaderValue
     {
         private static readonly HttpHeaderParser<NameValueHeaderValue> SingleValueParser
-            = new GenericHeaderParser<NameValueHeaderValue>(false, GetNameValueLength!);
+            = new GenericHeaderParser<NameValueHeaderValue>(false, GetNameValueLength);
         internal static readonly HttpHeaderParser<NameValueHeaderValue> MultipleValueParser
-            = new GenericHeaderParser<NameValueHeaderValue>(true, GetNameValueLength!);
+            = new GenericHeaderParser<NameValueHeaderValue>(true, GetNameValueLength);
 
         private StringSegment _name;
         private StringSegment _value;

src/Http/Headers/src/RangeConditionHeaderValue.cs

@@ -11,7 +11,7 @@ namespace Microsoft.Net.Http.Headers
     public class RangeConditionHeaderValue
     {
         private static readonly HttpHeaderParser<RangeConditionHeaderValue> Parser
-            = new GenericHeaderParser<RangeConditionHeaderValue>(false, GetRangeConditionLength!);
+            = new GenericHeaderParser<RangeConditionHeaderValue>(false, GetRangeConditionLength);
 
         private DateTimeOffset? _lastModified;
         private EntityTagHeaderValue? _entityTag;

src/Http/Headers/src/RangeHeaderValue.cs

@@ -13,7 +13,7 @@ namespace Microsoft.Net.Http.Headers
     public class RangeHeaderValue
     {
         private static readonly HttpHeaderParser<RangeHeaderValue> Parser
-            = new GenericHeaderParser<RangeHeaderValue>(false, GetRangeLength!);
+            = new GenericHeaderParser<RangeHeaderValue>(false, GetRangeLength);
 
         private StringSegment _unit;
         private ICollection<RangeItemHeaderValue>? _ranges;

src/Http/Headers/src/SetCookieHeaderValue.cs

@@ -33,9 +33,9 @@ namespace Microsoft.Net.Http.Headers
         private const string ExpiresDateFormat = "r";
 
         private static readonly HttpHeaderParser<SetCookieHeaderValue> SingleValueParser
-            = new GenericHeaderParser<SetCookieHeaderValue>(false, GetSetCookieLength!);
+            = new GenericHeaderParser<SetCookieHeaderValue>(false, GetSetCookieLength);
         private static readonly HttpHeaderParser<SetCookieHeaderValue> MultipleValueParser
-            = new GenericHeaderParser<SetCookieHeaderValue>(true, GetSetCookieLength!);
+            = new GenericHeaderParser<SetCookieHeaderValue>(true, GetSetCookieLength);
 
         private StringSegment _name;
         private StringSegment _value;

src/Http/Headers/src/StringWithQualityHeaderValue.cs

@@ -13,9 +13,9 @@ namespace Microsoft.Net.Http.Headers
     public class StringWithQualityHeaderValue
     {
         private static readonly HttpHeaderParser<StringWithQualityHeaderValue> SingleValueParser
-            = new GenericHeaderParser<StringWithQualityHeaderValue>(false, GetStringWithQualityLength!);
+            = new GenericHeaderParser<StringWithQualityHeaderValue>(false, GetStringWithQualityLength);
         private static readonly HttpHeaderParser<StringWithQualityHeaderValue> MultipleValueParser
-            = new GenericHeaderParser<StringWithQualityHeaderValue>(true, GetStringWithQualityLength!);
+            = new GenericHeaderParser<StringWithQualityHeaderValue>(true, GetStringWithQualityLength);
 
         private StringSegment _value;
         private double? _quality;

src/Http/Http.Extensions/src/HttpResponseJsonExtensions.cs

@@ -28,7 +28,7 @@ namespace Microsoft.AspNetCore.Http
         [SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "Required to maintain compatibility")]
         public static Task WriteAsJsonAsync<TValue>(
             this HttpResponse response,
-            [AllowNull] TValue value,
+            TValue value,
             CancellationToken cancellationToken = default)
         {
             return response.WriteAsJsonAsync<TValue>(value, options: null, contentType: null, cancellationToken);
@@ -47,7 +47,7 @@ namespace Microsoft.AspNetCore.Http
         [SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "Required to maintain compatibility")]
         public static Task WriteAsJsonAsync<TValue>(
             this HttpResponse response,
-            [AllowNull] TValue value,
+            TValue value,
             JsonSerializerOptions? options,
             CancellationToken cancellationToken = default)
         {
@@ -68,7 +68,7 @@ namespace Microsoft.AspNetCore.Http
         [SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "Required to maintain compatibility")]
         public static Task WriteAsJsonAsync<TValue>(
             this HttpResponse response,
-            [AllowNull] TValue value,
+            TValue value,
             JsonSerializerOptions? options,
             string? contentType,
             CancellationToken cancellationToken = default)
@@ -81,7 +81,7 @@ namespace Microsoft.AspNetCore.Http
             options ??= ResolveSerializerOptions(response.HttpContext);
 
             response.ContentType = contentType ?? JsonConstants.JsonContentTypeWithCharset;
-            return JsonSerializer.SerializeAsync<TValue>(response.Body, value!, options, cancellationToken);
+            return JsonSerializer.SerializeAsync<TValue>(response.Body, value, options, cancellationToken);
         }
 
         /// <summary>

src/Http/Http.Extensions/test/HttpResponseJsonExtensionsTests.cs

@@ -44,7 +44,7 @@ namespace Microsoft.AspNetCore.Http.Extensions.Tests
             context.Response.Body = body;
 
             // Act
-            await context.Response.WriteAsJsonAsync<Uri>(value: null);
+            await context.Response.WriteAsJsonAsync<Uri?>(value: null);
 
             // Assert
             Assert.Equal(JsonConstants.JsonContentTypeWithCharset, context.Response.ContentType);

src/Http/Http.Features/src/FeatureCollection.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 
 namespace Microsoft.AspNetCore.Http.Features
@@ -94,10 +93,9 @@ namespace Microsoft.AspNetCore.Http.Features
             }
         }
 
-        [return: MaybeNull]
+        public TFeature? Get<TFeature>()
-        public TFeature Get<TFeature>()
         {
-            return (TFeature)this[typeof(TFeature)];
+            return (TFeature?)this[typeof(TFeature)];
         }
 
         public void Set<TFeature>(TFeature instance)

src/Http/Http.Features/src/FeatureReference.cs

@@ -1,31 +1,28 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Diagnostics.CodeAnalysis;
-
 namespace Microsoft.AspNetCore.Http.Features
 {
     public struct FeatureReference<T>
     {
-        private T _feature;
+        private T? _feature;
         private int _revision;
 
-        private FeatureReference(T feature, int revision)
+        private FeatureReference(T? feature, int revision)
         {
             _feature = feature;
             _revision = revision;
         }
 
-        public static readonly FeatureReference<T> Default = new FeatureReference<T>(default(T)!, -1);
+        public static readonly FeatureReference<T> Default = new FeatureReference<T>(default(T), -1);
 
-        [return: MaybeNull]
+        public T? Fetch(IFeatureCollection features)
-        public T Fetch(IFeatureCollection features)
         {
             if (_revision == features.Revision)
             {
                 return _feature;
             }
-            _feature = (T)features[typeof(T)]!;
+            _feature = (T)features[typeof(T)];
             _revision = features.Revision;
             return _feature;
         }

src/Http/Http.Features/src/FeatureReferences.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 
 namespace Microsoft.AspNetCore.Http.Features
@@ -37,8 +36,7 @@ namespace Microsoft.AspNetCore.Http.Features
         // be able to pass ref values that "dot through" the TCache struct memory, 
         // if it was a Property then that getter would return a copy of the memory
         // preventing the use of "ref"
-        [AllowNull, MaybeNull]
+        public TCache? Cache;
-        public TCache Cache;
 
         // Careful with modifications to the Fetch method; it is carefully constructed for inlining
         // See: https://github.com/aspnet/HttpAbstractions/pull/704
@@ -61,10 +59,10 @@ namespace Microsoft.AspNetCore.Http.Features
         //
         // Generally Fetch is called at a ratio > x4 of UpdateCached so this is a large gain
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public TFeature Fetch<TFeature, TState>(
+        public TFeature? Fetch<TFeature, TState>(
-            [AllowNull, MaybeNull] ref TFeature cached,
+            ref TFeature? cached,
             TState state,
-            Func<TState, TFeature> factory) where TFeature : class?
+            Func<TState, TFeature?> factory) where TFeature : class?
         {
             var flush = false;
             var revision = Collection?.Revision ?? ContextDisposed();
@@ -80,7 +78,7 @@ namespace Microsoft.AspNetCore.Http.Features
         }
 
         // Update and cache clearing logic, when the fast-path in Fetch isn't applicable
-        private TFeature UpdateCached<TFeature, TState>(ref TFeature cached, TState state, Func<TState, TFeature> factory, int revision, bool flush) where TFeature : class?
+        private TFeature? UpdateCached<TFeature, TState>(ref TFeature? cached, TState state, Func<TState, TFeature?> factory, int revision, bool flush) where TFeature : class?
         {
             if (flush)
             {
@@ -108,8 +106,8 @@ namespace Microsoft.AspNetCore.Http.Features
             return cached;
         }
 
-        public TFeature Fetch<TFeature>([AllowNull, MaybeNull] ref TFeature cached, Func<IFeatureCollection, TFeature> factory)
+        public TFeature? Fetch<TFeature>(ref TFeature? cached, Func<IFeatureCollection, TFeature?> factory)
-            where TFeature : class? => Fetch(ref cached!, Collection, factory);
+            where TFeature : class? => Fetch(ref cached, Collection, factory);
 
         private static int ContextDisposed()
         {

src/Http/Http/src/Builder/ApplicationBuilder.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
@@ -58,8 +57,7 @@ namespace Microsoft.AspNetCore.Builder
 
         public IDictionary<string, object?> Properties { get; }
 
-        [return: MaybeNull]
+        private T? GetProperty<T>(string key)
-        private T GetProperty<T>(string key)
         {
             return Properties.TryGetValue(key, out var value) ? (T)value : default(T);
         }