Missing warning for unreachable arm in the presence of an intermediate when clause

[alrz]

Please provide a succinct description of the issue.

Repro steps

let f value b = match value  with
                | (true, true) -> -1
                | _ when b -> 2
                | (true, false) -> 3
                | (true, _) -> 4 // expected warning

Expected behavior

warning FS0026: This rule will never be matched for the last arm

Actual behavior

No warning about unreachable arm

[vzarytovskii]

I can see the warning on the 7.0.100+ FSI, @alrz which compiler/fsi version are you using?

[alrz]

Thanks. I'm using FSharp.Core 6.0.1 FWIW.

[vzarytovskii]

Thanks. I'm using FSharp.Core 6.0.1 FWIW.

I will check what was the fix and whether it was backported to 6.0.x

[alrz]

That would actually help, I'm trying out the same clause-by-clause approach in C# to handle "problematic" when clauses and sounds like I managed to port an old bug. Could it be #11993? Because that does change the detection method.