Proposed changes for enhancement:

appveyor.yml

@@ -1,6 +1,8 @@
 #version should be only changed with RELEASE eminent, see RELEASE.md
 version: 2.4.{build}
 
+image: Visual Studio 2017
+
 clone_depth: 1
 pull_requests:
   do_not_increment_build_number: true

src/CommandLine/CommandLine.csproj

@@ -14,7 +14,7 @@
     <Authors>gsscoder;nemec;ericnewton76</Authors>
     <Title>Command Line Parser Library</Title>
     <Version Condition="'$(VersionSuffix)' != ''">$(VersionSuffix)</Version>
-    <Version Condition="'$(VersionSuffix)' == ''">2.4.0</Version>
+    <Version Condition="'$(VersionSuffix)' == ''">0.0.0</Version>
     <Description Condition="'$(BuildTarget)' != 'fsharp'">Terse syntax C# command line parser for .NET.  For FSharp support see CommandLineParser.FSharp.  The Command Line Parser Library offers to CLR applications a clean and concise API for manipulating command line arguments and related tasks.</Description>
     <Description Condition="'$(BuildTarget)' == 'fsharp'">Terse syntax C# command line parser for .NET with F# support. The Command Line Parser Library offers to CLR applications a clean and concise API for manipulating command line arguments and related tasks.</Description>
     <Copyright>Copyright (c) 2005 - 2018 Giacomo Stelluti Scala &amp; Contributors</Copyright>
@@ -35,7 +35,7 @@
     </Content>
   </ItemGroup>
 
-  <ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' != 'net40' and '$(BuildTarget)' == 'fsharp'">
     <PackageReference Include="FSharp.Core" Version="4.5.1" Condition="'$(BuildTarget)' == 'fsharp'" />
   </ItemGroup>
 

src/CommandLine/Core/ReflectionExtensions.cs

@@ -93,10 +93,6 @@ public static TargetType ToTargetType(this Type type)
 
         private static IEnumerable<Error> SetValue<T>(this SpecificationProperty specProp, T instance, object value)
         {
-            Action<Exception> fail = inner => {
-                throw new InvalidOperationException(CannotSetValueToTargetInstance, inner);
-            };
-
             try
             {
                 specProp.Property.SetValue(instance, value, null);
@@ -106,17 +102,16 @@ private static IEnumerable<Error> SetValue<T>(this SpecificationProperty specPro
             {
                 return new[] { new SetValueExceptionError(specProp.Specification.FromSpecification(), e.InnerException, value) };
             }
-            catch (Exception e)
+            catch (ArgumentException e)
             {
-                 return new[] { new SetValueExceptionError(specProp.Specification.FromSpecification(), e, value) };
+                var argEx = new ArgumentException(InvalidAttributeConfigurationError.ErrorMessage, e);
+
+                return new[] { new SetValueExceptionError(specProp.Specification.FromSpecification(), argEx, value) };
             }
-            catch(ArgumentException e)
+            catch (Exception e)
             {
-                var argEx = new ArgumentException(InvalidAttributeConfigurationError.ErrorMessage, e);
-                fail(argEx);
+                return new[] { new SetValueExceptionError(specProp.Specification.FromSpecification(), e, value) };
             }
-
-            return instance;
         }
 
         public static object CreateEmptyArray(this Type type)
@@ -215,4 +210,4 @@ public static bool IsPrimitiveEx(this Type type)
                 || Convert.GetTypeCode(type) != TypeCode.Object;
         }
     }
-}
+}

src/CommandLine/Error.cs

@@ -64,8 +64,7 @@ public enum ErrorType
         /// <summary>
         /// Value of <see cref="CommandLine.SetValueExceptionError"/> type.
         /// </summary>
-        SetValueExceptionError
-        VersionRequestedError,
+        SetValueExceptionError,
         /// <summary>
         /// Value of <see cref="CommandLine.InvalidAttributeConfigurationError"/> type.
         /// </summary>
@@ -511,6 +510,18 @@ public object Value
         {
             get { return value; }
         }
+    }
 
+    /// <summary>
+    /// Models an error generated when an invalid token is detected.
+    /// </summary>
+    public sealed class InvalidAttributeConfigurationError : Error
+    {
+        public const string ErrorMessage = "Check if Option or Value attribute values are set properly for the given type.";
+
+        internal InvalidAttributeConfigurationError()
+            : base(ErrorType.InvalidAttributeConfigurationError, true)
+        {
+        }
     }
-}
+}

tests/CommandLine.Tests/Unit/Core/InstanceBuilderTests.cs

@@ -1007,6 +1007,22 @@ public void Parse_option_with_exception_thrown_from_setter_generates_SetValueExc
             // Teardown
         }
 
+        [Fact]
+        public void Parse_default_bool_type_string_SetValueExceptionError()
+        {
+            // Fixture setup
+            string name = nameof(Options_With_InvalidDefaults.FileName).ToLower();
+            var expectedResult = new[] { new SetValueExceptionError(new NameInfo("", name),
+                new ArgumentException(InvalidAttributeConfigurationError.ErrorMessage), "bad") };
+
+            // Exercize system 
+            var result = InvokeBuild<Options_With_InvalidDefaults>(
+                new[] { name, "bad" });
+
+            // Verify outcome
+            ((NotParsed<Options_With_InvalidDefaults>)result).Errors.Should().BeEquivalentTo(expectedResult);
+        }
+
 
         [Theory]
         [InlineData(new[] { "--stringvalue", "x-" }, "x-")]
@@ -1133,20 +1149,6 @@ public void Parse_TimeSpan()
             // Teardown
         }
 
-        [Fact]
-        public void Build_DefaultBoolTypeString_ThrowsInvalidOperationException()
-        {
-            // Exercize system 
-            Action test = () => InvokeBuild<Options_With_InvalidDefaults>(
-                new string[] { });
-
-            // Verify outcome
-            test.ShouldThrow<InvalidOperationException>()
-                .WithMessage(ReflectionExtensions.CannotSetValueToTargetInstance)
-                .WithInnerException<ArgumentException>()
-                .WithInnerMessage(InvalidAttributeConfigurationError.ErrorMessage);
-        }
-
 
         [Fact]
         public void OptionClass_IsImmutable_HasNoCtor()
@@ -1163,7 +1165,7 @@ private class ValueWithNoSetterOptions
         }
 
 
-        public static IEnumerable<object> RequiredValueStringData
+        public static IEnumerable<object[]> RequiredValueStringData
         {
             get
             {