public void GetFieldIndex_ShouldFind()
        {
            var comp    = new ExpressionCompiler <Action>();
            var fieldFi = typeof(Obj).GetField("Field");

            var objVar     = comp.Variable <Obj>("obj");
            var realIndex  = comp.Field(objVar, fieldFi);
            var foundIndex = comp.GetFieldIndex(fieldFi);

            Assert.Equal(realIndex, foundIndex);
        }