Not picking up ambiguous arg matchers properly

[dtchepak]

public interface ICalculator { int Add(int a, int b); }

[Test] public void a_test() {
    var calculator = Substitute.For<ICalculator>();
    calculator.Add(0, Arg.Any<int>()).Returns(5);
    Assert.AreEqual(5, calculator.Add(0, 1));        
}

This test fails at the Assert.AreEqual because it gets 0, not 5.

I expected to get an AmbiguousArgumentsException because it could not tell which argument the Arg.Any<int>() arg matcher applied to. Either that or have the test pass because I called Add(0, 1) which I stubbed to give 5.

[dtchepak]

Repro test case.

[AnthonyEgerton]

Fixed by 8d8aebf