refactor

Author: smdn

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection/MemberInfoNullableMetadataExtensions.cs

@@ -0,0 +1,67 @@
+// SPDX-FileCopyrightText: 2022 smdn <smdn@smdn.jp>
+// SPDX-License-Identifier: MIT
+using System;
+using System.Linq;
+using System.Reflection;
+
+namespace Smdn.Reflection;
+
+internal static class MemberInfoNullableMetadataExtensions {
+  private static bool IsNullableAttribute(CustomAttributeData attr)
+    => "System.Runtime.CompilerServices.NullableAttribute".Equals(attr.AttributeType.FullName, StringComparison.Ordinal);
+
+  private static bool IsNullableContextAttribute(CustomAttributeData attr)
+    => "System.Runtime.CompilerServices.NullableContextAttribute".Equals(attr.AttributeType.FullName, StringComparison.Ordinal);
+
+  internal static NullableMetadataValue? GetNullableAttributeMetadataValue(this MemberInfo memberOrType)
+  {
+    var data = memberOrType.CustomAttributes.FirstOrDefault(IsNullableAttribute);
+
+    if (data is null)
+      return null;
+
+    return (NullableMetadataValue?)(byte?)data.ConstructorArguments[0].Value;
+  }
+
+  internal static NullableMetadataValue? GetNullableContextAttributeMetadataValue(this MemberInfo memberOrType)
+  {
+    if (
+      memberOrType is Type genericParameter &&
+#if SYSTEM_TYPE_ISGENERICMETHODPARAMETER
+      genericParameter.IsGenericMethodParameter &&
+#else
+      genericParameter.DeclaringMethod is not null &&
+      genericParameter.IsGenericParameter &&
+#endif
+      GetMetadataValue(genericParameter.DeclaringMethod!, out var valueOfGenericParameter)
+    ) {
+      return valueOfGenericParameter;
+    }
+
+    MemberInfo? m = memberOrType;
+
+    for (; ; ) {
+      if (GetMetadataValue(m, out var value))
+        return value;
+      if ((m = m!.DeclaringType) is null)
+        return null;
+
+      // retry against to the outer type
+      continue;
+    }
+
+    static bool GetMetadataValue(MemberInfo memberOrType, out NullableMetadataValue? value)
+    {
+      var data = memberOrType.CustomAttributes.FirstOrDefault(IsNullableContextAttribute);
+
+      if (data is null) {
+        value = null;
+        return false;
+      }
+
+      value = (NullableMetadataValue?)(byte?)data.ConstructorArguments[0].Value;
+
+      return value.HasValue;
+    }
+  }
+}

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection/NullableMetadataValue.cs

@@ -0,0 +1,14 @@
+// SPDX-FileCopyrightText: 2022 smdn <smdn@smdn.jp>
+// SPDX-License-Identifier: MIT
+using System;
+using System.Linq;
+using System.Reflection;
+
+namespace Smdn.Reflection;
+
+// ref: https://github.com/dotnet/roslyn/blob/main/docs/features/nullable-metadata.md
+internal enum NullableMetadataValue : byte {
+  Oblivious = 0,
+  NotAnnotated = 1,
+  Annotated = 2,
+}

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection/TypeGenericParameterExtensions.cs

@@ -23,63 +23,12 @@ public static bool HasGenericParameterNotNullConstraint(this Type genericParamet
   {
     ValidateGenericParameterArgument(genericParameter, nameof(genericParameter));
 
-    var attrNullable = genericParameter.CustomAttributes.FirstOrDefault(IsNullableAttribute);
-    var attrNullableContext = FindNullableContextAttribute(genericParameter);
-
-    const byte notAnnotated = 1;
-
-    if (attrNullableContext is not null && notAnnotated.Equals(attrNullableContext.ConstructorArguments[0].Value))
+    if (genericParameter.GetNullableContextAttributeMetadataValue() == NullableMetadataValue.NotAnnotated)
       // `#nullable enable` context
-      return attrNullable is null;
+      return genericParameter.GetNullableAttributeMetadataValue() == null;
     else
       // `#nullable disable` context
-      return attrNullable is not null && notAnnotated.Equals(attrNullable.ConstructorArguments[0].Value);
-  }
-
-  private static bool IsNullableAttribute(CustomAttributeData attr)
-    => "System.Runtime.CompilerServices.NullableAttribute".Equals(attr.AttributeType.FullName, StringComparison.Ordinal);
-
-  private static bool IsNullableContextAttribute(CustomAttributeData attr)
-    => "System.Runtime.CompilerServices.NullableContextAttribute".Equals(attr.AttributeType.FullName, StringComparison.Ordinal);
-
-  private static bool TryGetNullableContextAttribute(
-    MemberInfo member,
-#if NULL_STATE_STATIC_ANALYSIS_ATTRIBUTES
-    [NotNullWhen(true)]
-#endif
-    out CustomAttributeData? attrNullableContext
-  )
-  {
-    attrNullableContext = member.CustomAttributes.FirstOrDefault(IsNullableContextAttribute);
-
-    return attrNullableContext is not null;
-  }
-
-  private static CustomAttributeData? FindNullableContextAttribute(Type genericParameter)
-  {
-    if (
-#if SYSTEM_TYPE_ISGENERICMETHODPARAMETER
-      genericParameter.IsGenericMethodParameter &&
-#else
-      genericParameter.DeclaringMethod is not null &&
-      genericParameter.IsGenericParameter &&
-#endif
-      TryGetNullableContextAttribute(genericParameter.DeclaringMethod!, out var methodAttr)
-    ) {
-      return methodAttr;
-    }
-
-    Type? t = genericParameter;
-
-    for (; ; ) {
-      if ((t = t!.DeclaringType) is null)
-        return null;
-      if (TryGetNullableContextAttribute(t, out var typeAttr))
-        return typeAttr;
-
-      // retry against to the outer type
-      continue;
-    }
+      return genericParameter.GetNullableAttributeMetadataValue() == NullableMetadataValue.NotAnnotated;
   }
 
   public static bool HasGenericParameterNoConstraints(this Type genericParameter)