Detect and reject an "argument constraint factory method" that produces two constraints

It’s a weird situation to be in, but if it comes up, we should complain about it.

Specifically, this spec fails, because no exception is thrown (we just use the first constraint, not even the one that’s returned from the method):

[Scenario]
public static void ConstraintFactoryThatMakesTwoConstraints(
    IHaveAnObjectParameter fake,
    Func<object> constraintFactory,
    Exception exception)
{
    "Given a fake"
        .x(() => fake = A.Fake<IHaveAnObjectParameter>());

    "And a delegate that produces two constraints"
        .x(() => constraintFactory = () =>
            {
                A<object>.That.Matches(i => i is object);
                return A<object>.That.Matches(i => i is null);
            });

    "When I try to configure a method of the fake with this delegate"
        .x(() => exception = Record.Exception(() => A.CallTo(() => fake.Bar(constraintFactory())).Returns(1)));

    "Then the call configuration throws a FakeConfigurationException"
        .x(() => exception.Should().BeAnExceptionOfType<FakeConfigurationException>());
}

(Of course, if we weren’t using a method to create constraints, and just specifying one inline via an expression, it’s only possible to create a single constraint.)

[thomaslevesque]

Good point!

(As an aside, maybe we should be throwing a FakeConfigurationException.)

Maybe. I don’t think we’re very consistent in the types of exceptions we throw…

[blairconrad]

This change has been released as part of FakeItEasy 5.3.0.