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Unexpected FS0812 when property has same name as DU case #16646

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cmeeren opened this issue Feb 2, 2024 · 4 comments · Fixed by #17088
Closed

Unexpected FS0812 when property has same name as DU case #16646

cmeeren opened this issue Feb 2, 2024 · 4 comments · Fixed by #17088
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Area-Diagnostics mistakes and possible improvements to diagnostics Feature Improvement Theme-Simple-F# A cross-community initiative called "Simple F#", keeping people in the sweet spot of the language.
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@cmeeren
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cmeeren commented Feb 2, 2024

Consider this code:

type MyId =
    | IdA of int
    | IdB of string

    member this.IdA =
        match this with
        | IdA x -> Some x
        | _ -> None


let onlyIdA (ids: MyId list) = ids |> List.choose _.IdA

The last line fails to compile with an error on _.IdA:

Error FS0812 : The syntax 'expr.id' may only be used with record labels, properties and fields

I would expect this to compile, since IdA is indeed a property.
@github-actions github-actions bot added this to the Backlog milestone Feb 2, 2024
@cmeeren
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cmeeren commented Feb 2, 2024 •
edited

This is not related to shorthand lambda, it also fails for normal lambdas:

let onlyIdA (ids: MyId list) = ids |> List.choose (fun x -> x.IdA)
                                                            ^^^^^

@0101 0101 added Impact-Low (Internal MS Team use only) Describes an issue with limited impact on existing code. Area-Diagnostics mistakes and possible improvements to diagnostics and removed Needs-Triage labels Feb 12, 2024
@0101
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0101 commented Feb 12, 2024

We should probably add a warning when defining a member with the same name as a DU case.

We might also want to fix the current error message.

@vzarytovskii
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It for sure has been like that for some time, definitely not a bug.

@vzarytovskii vzarytovskii added Feature Improvement Theme-Simple-F# A cross-community initiative called "Simple F#", keeping people in the sweet spot of the language. and removed Bug Impact-Low (Internal MS Team use only) Describes an issue with limited impact on existing code. labels Feb 20, 2024
@edgarfgp
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This is likely to be an error recovery issue FS0812 is reported using error(Error(.....)) so it will hide the previous raised error.

I think FS0812 should use errorR(Error(....)) to allow error cascading as expected

@edgarfgp edgarfgp mentioned this issue Feb 24, 2024
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@edgarfgp edgarfgp mentioned this issue Apr 25, 2024
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Area-Diagnostics mistakes and possible improvements to diagnostics Feature Improvement Theme-Simple-F# A cross-community initiative called "Simple F#", keeping people in the sweet spot of the language.
Projects
F# Compiler and Tooling
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Backlog
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@0101 @vzarytovskii @cmeeren @edgarfgp