Add JSON src-gen support for deserializing with parameterized ctors

eng/Versions.props

@@ -43,8 +43,8 @@
   </ItemGroup>
   <PropertyGroup>
     <!-- For source generator support we need to target a pinned version in order to be able to run on older versions of Roslyn -->
-    <MicrosoftCodeAnalysisCSharpWorkspacesVersion>3.8.0</MicrosoftCodeAnalysisCSharpWorkspacesVersion>
-    <MicrosoftCodeAnalysisVersion>3.8.0</MicrosoftCodeAnalysisVersion>
+    <MicrosoftCodeAnalysisCSharpWorkspacesVersion>3.9.0</MicrosoftCodeAnalysisCSharpWorkspacesVersion>
+    <MicrosoftCodeAnalysisVersion>3.9.0</MicrosoftCodeAnalysisVersion>
   </PropertyGroup>
   <PropertyGroup>
     <!-- Code analysis dependencies -->

src/libraries/System.Text.Json/Common/JsonConstants.cs

@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Text.Json
+{
+    internal static partial class JsonConstants
+    {
+        // The maximum number of parameters a constructor can have where it can be supported by the serializer.
+        public const int MaxParameterCount = 64;
+    }
+}

src/libraries/System.Text.Json/Common/ReflectionExtensions.cs

@@ -3,6 +3,7 @@
 
 using System.Diagnostics;
 using System.Reflection;
+using System.Collections.Generic;
 #if !BUILDING_SOURCE_GENERATOR
 using System.Diagnostics.CodeAnalysis;
 #endif
@@ -229,5 +230,85 @@ public static bool IsVirtual(this PropertyInfo? propertyInfo)
             Debug.Assert(propertyInfo != null);
             return propertyInfo != null && (propertyInfo.GetMethod?.IsVirtual == true || propertyInfo.SetMethod?.IsVirtual == true);
         }
+
+        public static bool IsKeyValuePair(this Type type, Type? keyValuePairType = null)
+        {
+            if (!type.IsGenericType)
+            {
+                return false;
+            }
+
+            // Work around not being able to use typeof(KeyValuePair<,>) directly during compile-time src gen type analysis.
+            keyValuePairType ??= typeof(KeyValuePair<,>);
+
+            Type generic = type.GetGenericTypeDefinition();
+            return generic == keyValuePairType;
+        }
+
+        public static bool TryGetDeserializationConstructor(
+#if !BUILDING_SOURCE_GENERATOR
+            [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+#endif
+            this Type type,
+            bool useDefaultCtorInAnnotatedStructs,
+            out ConstructorInfo? deserializationCtor)
+        {
+            ConstructorInfo? ctorWithAttribute = null;
+            ConstructorInfo? publicParameterlessCtor = null;
+            ConstructorInfo? lonePublicCtor = null;
+
+            ConstructorInfo[] constructors = type.GetConstructors(BindingFlags.Public | BindingFlags.Instance);
+
+            if (constructors.Length == 1)
+            {
+                lonePublicCtor = constructors[0];
+            }
+
+            foreach (ConstructorInfo constructor in constructors)
+            {
+                if (HasJsonConstructorAttribute(constructor))
+                {
+                    if (ctorWithAttribute != null)
+                    {
+                        deserializationCtor = null;
+                        return false;
+                    }
+
+                    ctorWithAttribute = constructor;
+                }
+                else if (constructor.GetParameters().Length == 0)
+                {
+                    publicParameterlessCtor = constructor;
+                }
+            }
+
+            // For correctness, throw if multiple ctors have [JsonConstructor], even if one or more are non-public.
+            ConstructorInfo? dummyCtorWithAttribute = ctorWithAttribute;
+
+            constructors = type.GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance);
+            foreach (ConstructorInfo constructor in constructors)
+            {
+                if (HasJsonConstructorAttribute(constructor))
+                {
+                    if (dummyCtorWithAttribute != null)
+                    {
+                        deserializationCtor = null;
+                        return false;
+                    }
+
+                    dummyCtorWithAttribute = constructor;
+                }
+            }
+
+            // Structs will use default constructor if attribute isn't used.
+            if (useDefaultCtorInAnnotatedStructs && type.IsValueType && ctorWithAttribute == null)
+            {
+                deserializationCtor = null;
+                return true;
+            }
+
+            deserializationCtor = ctorWithAttribute ?? publicParameterlessCtor ?? lonePublicCtor;
+            return true;
+        }
     }
 }

src/libraries/System.Text.Json/gen/ClassType.cs

@@ -16,6 +16,6 @@ internal enum ClassType
         Enumerable = 4,
         Dictionary = 5,
         Nullable = 6,
-        Enum = 7,
+        Enum = 7
     }
 }

src/libraries/System.Text.Json/gen/ContextGenerationSpec.cs

@@ -21,7 +21,7 @@ internal sealed class ContextGenerationSpec
 
         public List<TypeGenerationSpec> RootSerializableTypes { get; } = new();
 
-        public HashSet<TypeGenerationSpec>? NullableUnderlyingTypes { get; } = new();
+        public HashSet<TypeGenerationSpec>? ImplicitlyRegisteredTypes { get; } = new();
 
         public List<string> ContextClassDeclarationList { get; init; }