Fix incomplete pattern matches over C# enums producing the wrong warning

[jwosty]

PR #4522 has a bug, causing it to always produce FS0104 for non-F#-defined enum. For example, the following code:

// System.DateTimeKind = | Unspecified = 0 | Utc = 1 | Local = 2
let f = function System.DateTimeKind.Unspecified -> 0

currently produces this compiler warning:

typecheck error FS0104: Enums may take values outside known cases. For example, the value 'enum<System.DateTimeKind> (1)' may indicate a case not covered by the pattern(s).

when it is supposed to produce:

typecheck error FS0025: Incomplete pattern matches on this expression. For example, the value 'System.DateTimeKind.Utc' may indicate a case not covered by the pattern(s).

This PR corrects the issue.

Thanks to @charlesroddie for identifying the bug.

[jwosty]

@dotnet-bot test this please

[jwosty]

I don't know where this function should be refactored to as I'm not very well versed in the compiler's file structure. PatternMatchCompilation.fs comes before TypeChecker.fs, but the former needs this function.

[smoothdeveloper]

(just an opinion) You can expose it for use in TypeChecker.fs, and replace the comment akin to "Comes from TypeChecker.fs, might move to more apropriate place later.".

This would be better than having the code duplicated, and unless it becomes used in a third place, the location is not too important.

[jwosty]

@smoothdeveloper I kind of like that idea actually. That way its pretty obvious that not much code depends on it.

[jwosty]

@cartermp What is the cause of the CI failure? It reports:

Exception: Yaaf.FSharp.Scripting.FsiEvaluationException: Error while compiling or executing fsharp snippet. ---> System.Exception: Operation failed. The error text has been printed in the error stream. To return the corresponding FSharpErrorInfo use the EvalInteractionNonThrowing, EvalScriptNonThrowing or EvalExpressionNonThrowing
... etc etc
System.Net.WebException: The remote server returned an error: (404) Not Found.
   at System.Net.WebClient.DownloadFile(Uri address, String fileName

[cartermp]

cc @matthid - sounds like a FAKE issue on CI?

[matthid]

@forki Is this the broken .NET SDK installer problem? Where is the other issue about that?

[forki]

I only know of Twitter discussion. And the urls worked for us again. /cc @davkean Matthias Dittrich <[email protected]> schrieb am Mi., 20. Juni 2018, 21:56:

…

@forki <https://github.com/forki> Is this the broken .NET SDK installer problem? Where is the other issue about that? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#5206 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AADgNAo-bN_BV37JUiU-mP1B73mDGQkGks5t-qkHgaJpZM4Uqo0M> .

[cartermp]

test Ubuntu16.04 Release_fcs Build Windows_NT Release_fcs Build

[cartermp]

test Windows_NT Release_fcs Build

[jwosty]

Thanks @cartermp! Now that CI is working... Requesting reviews 🙂 @dsyme @forki

[matthid]

So typical try again until it works error?

[cartermp]

@matthid jawohl!

[jwosty]

There's no more for me to do at the moment. Could this be considered for merge? @dsyme

[KevinRansom]

Thanks for this