result |> should be (ofCase <@ Ok @>) throws exception at runtime

[BryanWilhite]

Description

System.InvalidCastException
Unable to cast object of type 'Microsoft.FSharp.Core.FSharpResult`2[System.Tuple`2[System.Boolean,System.Text.Json.JsonElement],System.Text.Json.JsonException]' to type 'Microsoft.FSharp.Core.FSharpResult`2[System.Object,System.Object]'.
   at lambda_method25(Closure , Object )
   at FsUnit.Common.isOfCase@54.Invoke(a x)
   at NHamcrest.Core.CustomMatcher`1.Matches(T item)
   at Songhay.Dashboard.Bolero.Tests.SyndicationFeedTests.getAtomChannelTitle test(String elementName) 

Repro steps

    [<Theory>]
    [<InlineData(nameof GitHub)>]
    [<InlineData(nameof StackOverflow)>]
    let ``getAtomChannelTitle test`` elementName =
        let result: Result<(bool * JsonElement),JsonException> =
            appJsonDocument.RootElement
            |> SyndicationFeedUtility.getFeedElement elementName

        result |> should be (ofCase <@ Ok @>)

Related information

JetBrains Rider 2021.3.2
Build #RD-213.6461.51, built on December 22, 2021
Licensed to Bryan Wilhite
Subscription is active until August 12, 2022.
Runtime version: 11.0.13+7-b1751.21 amd64
VM: Dynamic Code Evolution 64-Bit Server VM by JetBrains s.r.o.
Linux 5.13.0-27-generic
.NET 6.0.1
GC: G1 Young Generation, G1 Old Generation
Memory: 1500M
Cores: 8
Registry:
    ide.new.project.model.index.case.sensitivity=true
    indexing.enable.entity.provider.based.indexing=false
    rdclient.asyncActions=false

Non-Bundled Plugins:
    com.settler.rider.specflow (1.10.2)
    com.intellij.plugins.vscodekeymap (213.5744.3)
    com.intellij.resharper.azure (3.50.0.1314-2021.3)

Current Desktop: ubuntu:GNOME

[sergey-tihon]

This discussion should help #190 (comment)

As you error message say

Unable to cast object of type 'Microsoft.FSharp.Core.FSharpResult2[System.Tuple2[System.Boolean,System.Text.Json.JsonElement],System.Text.Json.JsonException]' to type 'Microsoft.FSharp.Core.FSharpResult`2[System.Object,System.Object]'.

result has type Microsoft.FSharp.Core.FSharpResult2[System.Tuple2[System.Boolean,System.Text.Json.JsonElement],System.Text.Json.JsonException]

Ok has type Microsoft.FSharp.Core.FSharpResult2[System.Object,System.Object](compiler was not able to infer generic params of Result type just fromOk`

So in runtime FsUnit see 2 objects with different types and they cannot be equal.

[CaptnCodr]

You may have to add further type declarations to your code.

Just try following:

result |> should be (ofCase <@ Result<(bool * JsonElement),JsonException>.Ok @>)

[BryanWilhite]

excellent! many thanks @sergey-tihon and @CaptnCodr!

it is working as expected: