error CS0121: "The call is ambiguous between the following methods or properties" after upgrade from net5.0 to 6.0.0-rc.1.21451.3

[christothes]

Description

For code that compiled with no errors on .net5, the following errors appeared after upgrading to 6.0.0-rc.1.21451.3:

error CS0121: The call is ambiguous between the following methods or properties: 'Assert.That<TActual>(ActualValueDelegate<TActual>, IResolveConstraint)' and 'Assert.That<TActual>(TActual, IResolveConstraint)'

Reproduction Steps

Attempt to compile the following NUnit assertion

Assert.That(() => Foo.Bar(), Throws.InstanceOf<ArgumentNullException>());

public class Foo
{
	public void Bar()
	{
		throw new ArgumentNullException();
	}
}

Expected behavior

Code compiles without error

Actual behavior

error CS0121: The call is ambiguous between the following methods or properties: 'Assert.That(ActualValueDelegate, IResolveConstraint)' and 'Assert.That(TActual, IResolveConstraint)'

Regression?

Does not reproduce with .net 5.0.10

Known Workarounds

No response

Configuration

6.0.0-rc.1.21451.3
Windows 11 x64

Other information

No response

[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.

[stephentoub]

cc: @cston

[cston]

Thanks for reporting this @christothes.

This looks like a duplicate of #56167 that should be fixed in .NET 6 RC2.