Squashed commit of the following:

commit 13175cf
Author: smdn <smdn@smdn.jp>
Date:   Mon Mar 7 23:07:28 2022 +0900

    fix expected value running on .NET Framework

commit bf4d129
Author: smdn <smdn@smdn.jp>
Date:   Mon Mar 7 23:06:47 2022 +0900

    add support for generating expected value from field, method or property
Merge remote-tracking branch 'refs/remotes/origin/main' into main

Author: smdn

tests/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating.Tests.csproj

@@ -8,4 +8,17 @@ SPDX-License-Identifier: MIT
     <RootNamespace>Smdn.Reflection.ReverseGenerating</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Smdn.Reflection.ReverseGenerating\Smdn.Reflection.ReverseGenerating.csproj" />
+    <PackageReference
+      Include="System.Runtime.InteropServices.RuntimeInformation"
+      Version="4.3.0"
+      Condition = "(
+        $(TargetFramework.StartsWith('net45')) or
+        $(TargetFramework.StartsWith('net46')) or
+        $(TargetFramework.StartsWith('net47'))
+      )"
+    />
+  </ItemGroup>
 </Project>

tests/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating/Generator.Attributes.cs

@@ -46,7 +46,25 @@ class AttributeTargetsMember {
 
         class AttributeTargetsReturnValue {
 #if NETFRAMEWORK
-          [return: AttributeTestCase("[return: System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.Bool)]")]
+          static string M0_ExpectedResult =>
+            RuntimeInformation.FrameworkDescription.StartsWith(".NET Framework", StringComparison.Ordinal)
+              ? "[return: System.Runtime.InteropServices.MarshalAs(" +
+                "System.Runtime.InteropServices.UnmanagedType.Bool, "+
+                "ArraySubType = default(System.Runtime.InteropServices.UnmanagedType), " +
+                "SizeParamIndex = 0, " +
+                "SizeConst = 0, " +
+                "IidParameterIndex = 0, " +
+                "SafeArraySubType = System.Runtime.InteropServices.VarEnum.VT_EMPTY" +
+                ")]"
+              : "[return: System.Runtime.InteropServices.MarshalAs(" +
+                "System.Runtime.InteropServices.UnmanagedType.Bool)" +
+                "]";
+
+          [return: AttributeTestCase(
+            expected: null,
+            ExpectedValueGeneratorType = typeof(AttributeTargetsReturnValue),
+            ExpectedValueGeneratorMemberName = nameof(M0_ExpectedResult)
+          )]
           [return: MarshalAs(UnmanagedType.Bool)]
           public bool M0() => throw new NotImplementedException();
 #endif

tests/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating/Generator.cs

@@ -10,7 +10,9 @@
 namespace Smdn.Reflection.ReverseGenerating;
 
 public abstract class GeneratorTestCaseAttribute : Attribute {
-  public string Expected { get; private set; }
+  private readonly string expectedValue;
+  public Type ExpectedValueGeneratorType { get; set; } = null;
+  public string ExpectedValueGeneratorMemberName { get; set; } = null;
   public bool TranslateLanguagePrimitiveTypeDeclaration { get; set; } = true;
   public bool MemberWithNamespace { get; set; } = true;
   public bool MemberWithDeclaringTypeName { get; set; } = false;
@@ -29,13 +31,34 @@ public abstract class GeneratorTestCaseAttribute : Attribute {
   public MethodBodyOption MethodBody { get; set; } = MethodBodyOption.EmptyImplementation;
   public string SourceLocation { get; }
 
+  public string Expected {
+    get {
+      if (ExpectedValueGeneratorType is null && ExpectedValueGeneratorMemberName is null)
+        return expectedValue;
+
+      var expectedValueGeneratorMember = ExpectedValueGeneratorType.GetMember(
+        ExpectedValueGeneratorMemberName,
+        MemberTypes.Field | MemberTypes.Method | MemberTypes.Property,
+        BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic
+      ).FirstOrDefault();
+
+      return expectedValueGeneratorMember switch {
+        FieldInfo f => (string)f.GetValue(obj: null),
+        MethodInfo m => (string)m.Invoke(obj: null, parameters: null),
+        PropertyInfo p => (string)p.GetGetMethod(nonPublic: true)?.Invoke(obj: null, parameters: null),
+        null => throw new InvalidOperationException($"member not found: {ExpectedValueGeneratorType.FullName}.{ExpectedValueGeneratorMemberName}"),
+        _ => throw new InvalidOperationException($"invalid member type: {ExpectedValueGeneratorType.FullName}.{ExpectedValueGeneratorMemberName}"),
+      };
+    }
+  }
+
   public GeneratorTestCaseAttribute(
     string expected,
     string sourceFilePath,
     int lineNumber
   )
   {
-    this.Expected = expected;
+    this.expectedValue = expected;
     this.SourceLocation = $"{Path.GetFileName(sourceFilePath)}:{lineNumber}";
   }
 }