From 15b5a6ce4bf34c03ef172e1e01eedd7e039cc5c4 Mon Sep 17 00:00:00 2001
From: "Kevin Ransom (msft)" <codecutter@hotmail.com>
Date: Wed, 7 Aug 2024 11:41:48 -0700
Subject: [PATCH] Update DefaultAugmentationAttribute (#17502)

* Update DefaultAugmentationAttribute

* readme
---
 docs/release-notes/.FSharp.Core/9.0.100.md                    | 2 +-
 src/FSharp.Core/prim-types.fs                                 | 4 ++--
 src/FSharp.Core/prim-types.fsi                                | 2 +-
 .../Conformance/Types/UnionTypes/UnionStructTypes.fs          | 1 +
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/docs/release-notes/.FSharp.Core/9.0.100.md b/docs/release-notes/.FSharp.Core/9.0.100.md
index 9438303a7ed..50d799c4c9e 100644
--- a/docs/release-notes/.FSharp.Core/9.0.100.md
+++ b/docs/release-notes/.FSharp.Core/9.0.100.md
@@ -8,6 +8,6 @@
 ### Changed
 * Change compiler default setting realsig+ when building assemblies ([Issue #17384](https://github.com/dotnet/fsharp/issues/17384), [PR #17378](https://github.com/dotnet/fsharp/pull/17385))
 * Change compiler default setting for compressedMetadata ([Issue #17379](https://github.com/dotnet/fsharp/issues/17379), [PR #17383](https://github.com/dotnet/fsharp/pull/17383))
-
+* Struct UnionCase doesn't seem to be a valid target for the DefaultAugmentationAttribute ([Issue #17499](https://github.com/dotnet/fsharp/issues/17499), [PR #17502](https://github.com/dotnet/fsharp/pull/17502))
 ### Breaking Changes
 
diff --git a/src/FSharp.Core/prim-types.fs b/src/FSharp.Core/prim-types.fs
index 211496b99d1..b5bcc6c28ba 100644
--- a/src/FSharp.Core/prim-types.fs
+++ b/src/FSharp.Core/prim-types.fs
@@ -90,7 +90,7 @@ namespace Microsoft.FSharp.Core
     type VolatileFieldAttribute() =
         inherit Attribute()
       
-    [<AttributeUsage (AttributeTargets.Class, AllowMultiple=false)>]  
+    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct, AllowMultiple=false)>]  
     [<Sealed>]
     type DefaultAugmentationAttribute(value:bool) = 
         inherit Attribute()
@@ -106,7 +106,7 @@ namespace Microsoft.FSharp.Core
     type CLIMutableAttribute() = 
         inherit Attribute()
 
-    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct , AllowMultiple=false)>]
+    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct, AllowMultiple=false)>]
     [<Sealed>]
     type AutoSerializableAttribute(value:bool) = 
         inherit Attribute()
diff --git a/src/FSharp.Core/prim-types.fsi b/src/FSharp.Core/prim-types.fsi
index 8b35a81e886..79b73df66e7 100644
--- a/src/FSharp.Core/prim-types.fsi
+++ b/src/FSharp.Core/prim-types.fsi
@@ -324,7 +324,7 @@ namespace Microsoft.FSharp.Core
     /// and accessor members for the generated CLI class for that type.</summary>
     ///
     /// <category>Attributes</category>
-    [<AttributeUsage (AttributeTargets.Class,AllowMultiple=false)>]  
+    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct,AllowMultiple=false)>]  
     [<Sealed>]
     type DefaultAugmentationAttribute =
         inherit Attribute
diff --git a/tests/FSharp.Compiler.ComponentTests/Conformance/Types/UnionTypes/UnionStructTypes.fs b/tests/FSharp.Compiler.ComponentTests/Conformance/Types/UnionTypes/UnionStructTypes.fs
index 574f1695d62..a202d3b03cb 100644
--- a/tests/FSharp.Compiler.ComponentTests/Conformance/Types/UnionTypes/UnionStructTypes.fs
+++ b/tests/FSharp.Compiler.ComponentTests/Conformance/Types/UnionTypes/UnionStructTypes.fs
@@ -778,6 +778,7 @@ type Foo =
 
 let foo = [Baz 42; Bat; Batman]
 printf "%A" foo"""
+        |> withLangVersionPreview
         |> asExe
         |> compile
         |> shouldSucceed