Local methods and delegates aren't populating ParameterInfo.DefaultValue

[JamesNK]

Description

ParameterInfo.DefaultValue isn't available with local methods (and I'm guessing delegates as well). In this ASP.NET Core feature we want to use the default value information to make decisions about how a delegate will be called. e.g. use the default value when calling the method if no other value is available.

[Fact]
public void DefaultValueTest()
{
    void TestAction([FromRoute] int foo1 = 5)
    {
    }

    var method = GetType().GetMethod(nameof(TestAction), BindingFlags.Instance | BindingFlags.NonPublic)!;
    var p1 = method.GetParameters();
    Console.WriteLine(p1[0].HasDefaultValue);
    Console.WriteLine(p1[0].DefaultValue);
    // true
    // 5

    var d = (Action<int>)TestAction;
    var p2 = d.Method.GetParameters();
    Console.WriteLine(p2[0].HasDefaultValue);
    Console.WriteLine(p2[0].DefaultValue);
    // false
    // DBNull.Value
}

private void TestAction([FromRoute] int foo1 = 5)
{
}

Configuration

Host (useful for support):
Version: 6.0.0-preview.2.21154.6
Commit: 3eaf1f316b

Regression?

No

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[JamesNK]

@halter73 @davidfowl

[jkotas]

Roslyn does not emit the default values, so reflection does not return them.

[cston]

Thanks @JamesNK.

This looks like a duplicate of #51518 which is being addressed in #53402.

[Youssef1313]

Indeed. I added a test for this issue in #53402