F# 9.0 Invalid sample for struct discriminated unions

[gewarren]

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Issue moved from MicrosoftDocs/feedback#4042

• Please respond to @ryanovic.

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From @ryanovic on Monday, January 6, 2025 2:17:34 PM

In the language reference document(Discriminated Unions) provided the following F# code example:

[<Struct>]
type Multicase =
    | Case1 of string
    | Case2 of int
    | Case3 of double

Which is not correct, and would not compile with the recent .net9 SDK(error FS3585: If a multicase union type is a struct, then all fields with the same name must be of the same type). According to the other article(What's new in F# 9) only fields which have the same name and type, can share the same memory location, so it will not work for string / int / double intersection.

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Document Details

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• ID: 6020749e-d91e-8a1b-5366-25b212baa31d
• Version Independent ID: 0f28f508-dc0f-c272-383e-ec768759fe16
• Content: Discriminated Unions - F#
• Content Source: docs/fsharp/language-reference/discriminated-unions.md
• Service: dotnet-fsharp
• GitHub Login: @KathleenDollard
• Microsoft Alias: kdollard

[gewarren]

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Issue moved from MicrosoftDocs/feedback#4042

• Please respond to @WELCOME[bot].

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From @WELCOME[bot] on Monday, January 6, 2025 2:17:38 PM

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