ofCase doesn't support generic union type
wenLiangcan opened this issue · comments
Description
Checking case of generic union type throws System.InvalidCastException.
Repro steps
type MyCase<'T> =
| Case1 of 'T
| Case2
let intCase1 = Case1 1
intCase1 |> should be (ofCase <@ Case1 @>)Expected behavior
The testing should be passed.
Actual behavior
The following exception is throwed.
Failed Test [49 ms]
Error Message:
System.InvalidCastException : Unable to cast object of type 'Case1[System.Int32]' to type 'MyCase`1[System.Object]'.
Stack Trace:
at lambda_method34(Closure , Object )
at FsUnit.Common.isOfCase@50.Invoke(a x)
at FsUnit.CustomConstraints.OfSameCaseConstraint.ApplyTo[TActual](TActual actual)
at NUnit.Framework.Assert.That[TActual](TActual actual, IResolveConstraint expression, String message, Object[] args)
at NUnit.Framework.Assert.That[TActual](TActual actual, IResolveConstraint expression)
at FsUnit.TopLevelOperators.should[a,a](FSharpFunc`2 f, a x, Object y)
Known workarounds
None.
Related information
- Windows 11
- FsUnit 4.0.6
- .NET 5
that is how type inference works in F#.
Compiler has no information to identify type of Case1 inside quotation, that is why it uses most generic one MyCase
in this case you have to manually specify type to help compiler
otherwise types are different and they should not be equal
@sergey-tihon Thanks, did not know this way to specify the concrete type for a case before.