Description

When using an expression containing a lifted operator, i.e. > on a null, the call to ExpressionVisitor.Visit fails.
This is probably because there is static bool operator<(int?, int?), it's only syntax sugar.
So

public bool M(int? i) => i > 42;

is transformed into

public bool M(Nullable<int> i)
{
    Nullable<int> num = i;
    int num2 = 42;
    return (num.GetValueOrDefault() > num2) & num.HasValue;
}

Complete minimal example reproducing the issue

public class TestObject
{
    public int? Prop { get; set; }
}

public class UnitTest
{
    [Fact]
    public void LiftedBinaryOperator()
    {
        var subject = new TestObject { Prop = 42 };
        subject.Should().Match<TestObject>(e => e.Prop > 43);
    }
}

Expected behavior:

Assertion should throw with a proper failure description.
E.g.

Xunit.Sdk.XunitException: 'Expected subject to match (e.Prop > Convert(43)), but found FluentAssertions.Specs.TestObject
{
    Prop = 42
}.'

Actual behavior:

System.InvalidOperationException: 'The binary operator GreaterThan is not defined for the types 'System.Nullable`1[System.Int32]' and 'System.Int32'.'

Versions

• Which version of Fluent Assertions are you using: master
• Which .NET runtime and version are you targeting? net 5.0