Account for generic types when determining accessibility

Author: layomia

src/libraries/Common/src/SourceGenerators/TypeModelHelper.cs

@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System;
 using System.Text;
 using Microsoft.CodeAnalysis;
 using System.Collections.Generic;
@@ -74,7 +73,7 @@ public static string ToIdentifierCompatibleSubstring(this ITypeSymbol type, bool
         /// </summary>
         public static string ToMinimalDisplayString(this ITypeSymbol type) => type.ToDisplayString(s_minimalDisplayFormat);
 
-        private static List<ITypeSymbol>? GetAllTypeArgumentsInScope(this INamedTypeSymbol type)
+        public static List<ITypeSymbol>? GetAllTypeArgumentsInScope(this INamedTypeSymbol type)
         {
             if (!type.IsGenericType)
             {

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.Parser.cs

@@ -9,6 +9,7 @@
 using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Operations;
+using SourceGenerators;
 
 namespace Microsoft.Extensions.Configuration.Binder.SourceGeneration
 {
@@ -87,6 +88,17 @@ static bool IsAccessibleFromGenBinders(ITypeSymbol type)
                         return IsAccessibleFromGenBinders(array.ElementType);
                     }
 
+                    if (type is INamedTypeSymbol namedType && namedType.GetAllTypeArgumentsInScope() is List<ITypeSymbol> typeArgsInScope)
+                    {
+                        foreach (ITypeSymbol genericArg in typeArgsInScope)
+                        {
+                            if (!IsAccessibleFromGenBinders(genericArg))
+                            {
+                                return false;
+                            }
+                        }
+                    }
+
                     return type.DeclaredAccessibility is Accessibility.Public or Accessibility.Internal or Accessibility.Friend;
                 }
             }

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/SourceGenerationTests/ConfigurationBinderTests.Generator.cs

@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
+using System.Collections.Generic;
 using Microsoft.Extensions.Configuration;
 using Xunit;
 
@@ -336,17 +338,51 @@ public void MemberAccessibility_InaccessibleNestedTypeAsRootConfig()
             var c2 = configuration.Get<InaccessibleClass_2>();
             var c3 = configuration.Get<InaccessibleClass_3>();
 
+            // Generic collections.
+
             configuration = TestHelpers
                 .GetConfigurationFromJsonString(@"{""Array"": [{""Value"":1}]}")
                 .GetSection("Array");
             var c4 = configuration.Get<InaccessibleClass_1[]>();
+            var c5 = configuration.Get<List<InaccessibleClass_1>>();
+
+            // Generic types.
+
+            Action<BinderOptions>? configureOptions = options => options.BindNonPublicProperties = true;
+            string GetNestedObjectPayload(string propName) => $$"""
+                {
+                    "{{propName}}": {
+                        "Value": 1
+                    }
+                }
+                """;
+
+            configuration = TestHelpers.GetConfigurationFromJsonString(GetNestedObjectPayload("item1"));
+            var c6 = configuration.Get<Dictionary<string, InaccessibleClass_1>>(configureOptions);
+
+            configuration = TestHelpers.GetConfigurationFromJsonString(GetNestedObjectPayload("protectedMember"));
+            var c7 = configuration.Get<AccessibleGenericClass<InaccessibleClass_1>>(configureOptions);
+            var c8 = configuration.Get<AccessibleGenericClass<InaccessibleClass_1>>(configureOptions);
+
+            configuration = TestHelpers.GetConfigurationFromJsonString(GetNestedObjectPayload("publicMember"));
+            var c9 = configuration.Get<InaccessibleGenericClass<AccessibleClass>>(configureOptions);
+            var c10 = configuration.Get<InaccessibleGenericClass<InaccessibleClass_1>>(configureOptions);
 #pragma warning disable SYSLIB1104
 
-            // Instead, there is a reflection fallback.
+            // Reflection fallback.
+
             Assert.Equal(1, c1.Value);
             Assert.Equal(1, c2.Value);
             Assert.Equal(1, c3.Value);
+            
             Assert.Equal(1, c4[0].Value);
+            Assert.Equal(1, c5[0].Value);
+            Assert.Equal(1, c6["item1"].Value);
+
+            Assert.Equal(1, c7.GetProtectedMember.Value);
+            Assert.Equal(1, c8.GetProtectedMember.Value);
+            Assert.Equal(1, c9.PublicMember.Value);
+            Assert.Equal(1, c10.PublicMember.Value);
         }
 
         private class InaccessibleClass_1()
@@ -362,5 +398,22 @@ protected internal class InaccessibleClass_3
 
             public int Value { get; }
         }
+
+        internal class AccessibleGenericClass<T>
+        {
+            protected T ProtectedMember { get; set; }
+
+            public T GetProtectedMember => ProtectedMember;
+        }
+
+        private class InaccessibleGenericClass<T>
+        {
+            public T PublicMember { get; set; }
+        }
+
+        public class AccessibleClass()
+        {
+            public int Value { get; set; }
+        }
     }
 }