AttributeTargets.Class and AttributeTargets.Struct can be targeted in an enum incorrectly

docs/release-notes/.FSharp.Compiler.Service/8.0.300.md

@@ -20,6 +20,7 @@
 * Enforce AttributeTargets on structs and classes ([PR #16790](https://github.com/dotnet/fsharp/pull/16790))
 * Parser: fix pattern range for idents with trivia ([PR #16824](https://github.com/dotnet/fsharp/pull/16824))
 * Fix broken code completion after a record type declaration ([PR #16813](https://github.com/dotnet/fsharp/pull/16813))
+* Enforce AttributeTargets on enums ([PR #16887](https://github.com/dotnet/fsharp/pull/16887))
 
 ### Added
 

docs/release-notes/.FSharp.Core/8.0.300.md

@@ -6,4 +6,5 @@
 ### Fixed
 
 * Preserve original stack traces in resumable state machines generated code if available. ([PR #16568](https://github.com/dotnet/fsharp/pull/16568))
-* Enforce AttributeTargets on structs and classes. Also update `RequireQualifiedAccessAttribute` and `AutoOpenAttribute` to use `AttributeTargets.Struct` ([PR #16790](https://github.com/dotnet/fsharp/pull/16790))
+* Enforce AttributeTargets on structs and classes. Also update `RequireQualifiedAccessAttribute` and `AutoOpenAttribute` to use `AttributeTargets.Struct` ([PR #16790](https://github.com/dotnet/fsharp/pull/16790))
+* Enforce AttributeTargets on enums. Also update `RequireQualifiedAccessAttribute` to use `AttributeTargets.Enum` ([PR #16887](https://github.com/dotnet/fsharp/pull/16887))

src/Compiler/Checking/CheckDeclarations.fs

@@ -2940,7 +2940,9 @@ module EstablishTypeDefinitionCores =
 
                     TFSharpTyconRepr (Construct.NewEmptyFSharpTyconData kind)
 
-            | SynTypeDefnSimpleRepr.Enum _ -> 
+            | SynTypeDefnSimpleRepr.Enum _ ->
+                if g.langVersion.SupportsFeature(LanguageFeature.EnforceAttributeTargets) then
+                    TcAttributesWithPossibleTargets false cenv envinner AttributeTargets.Enum synAttrs |> ignore
                 TFSharpTyconRepr (Construct.NewEmptyFSharpTyconData TFSharpEnum)
 
         // OK, now fill in the (partially computed) type representation

src/FSharp.Core/prim-types.fs

@@ -350,7 +350,7 @@ namespace Microsoft.FSharp.Core
     type RequiresExplicitTypeArgumentsAttribute() =
         inherit Attribute()
 
-    [<AttributeUsage(AttributeTargets.Class ||| AttributeTargets.Struct, AllowMultiple=false)>]
+    [<AttributeUsage(AttributeTargets.Class ||| AttributeTargets.Struct ||| AttributeTargets.Enum, AllowMultiple=false)>]
     [<Sealed>]
     type RequireQualifiedAccessAttribute() =
         inherit Attribute()

src/FSharp.Core/prim-types.fsi

@@ -898,7 +898,7 @@ namespace Microsoft.FSharp.Core
     /// type require explicit qualified access.</summary>
     ///
     /// <category>Attributes</category>
-    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct, AllowMultiple=false)>]  
+    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct ||| AttributeTargets.Enum, AllowMultiple=false)>]  
     [<Sealed>]
     type RequireQualifiedAccessAttribute =
         inherit Attribute

tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/CustomAttributes/AttributeUsage/AttributeTargetsIsEnum01.fs

@@ -0,0 +1,11 @@
+open System
+
+[<AttributeUsage(AttributeTargets.Enum)>]
+type CustomEnumAttribute() =
+    inherit Attribute()
+
+[<CustomEnum>]
+type Color =
+    | Red = 0
+    | Green = 1
+    | Blue = 2

tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/CustomAttributes/AttributeUsage/AttributeUsage.fs

@@ -519,4 +519,40 @@ module CustomAttributes_AttributeUsage =
             (Error 842, Line 11, Col 16, Line 11, Col 28, "This attribute is not valid for use on this language element")
             (Error 842, Line 14, Col 15, Line 14, Col 27, "This attribute is not valid for use on this language element")
             (Error 842, Line 17, Col 16, Line 17, Col 28, "This attribute is not valid for use on this language element")
+        ]
+
+    // SOURCE=AttributeTargetsIsEnum01.fs	# AttributeTargetsIsEnum01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"AttributeTargetsIsEnum01.fs"|])>]
+    let ``AttributeTargetsIsEnum01_fs`` compilation =
+        compilation
+        |> verifyCompile
+        |> shouldSucceed
+
+    // SOURCE=AttributeTargetsIsEnum01.fs	# AttributeTargetsIsEnum01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"AttributeTargetsIsEnum01.fs"|])>]
+    let ``AttributeTargetsIsEnum01_fs preview`` compilation =
+        compilation
+        |> withLangVersionPreview
+        |> verifyCompile
+        |> shouldSucceed
+
+    // SOURCE=E_AttributeTargetIsEnum01.fs	# E_AttributeTargetIsEnum01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"E_AttributeTargetIsEnum01.fs"|])>]
+    let ``E_AttributeTargetIsEnum01_fs`` compilation =
+        compilation
+        |> verifyCompile
+        |> shouldSucceed
+
+    // SOURCE=E_AttributeTargetIsEnum01.fs	# E_AttributeTargetIsEnum01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"E_AttributeTargetIsEnum01.fs"|])>]
+    let ``E_AttributeTargetIsEnum01_fs preview`` compilation =
+        compilation
+        |> withLangVersionPreview
+        |> verifyCompile
+        |> shouldFail
+        |> withDiagnostics [
+            (Error 842, Line 19, Col 3, Line 19, Col 15, "This attribute is not valid for use on this language element")
+            (Error 842, Line 20, Col 3, Line 20, Col 14, "This attribute is not valid for use on this language element")
+            (Error 842, Line 21, Col 3, Line 21, Col 18, "This attribute is not valid for use on this language element")
+            (Error 842, Line 22, Col 3, Line 22, Col 17, "This attribute is not valid for use on this language element")
         ]

tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/CustomAttributes/AttributeUsage/E_AttributeTargetIsEnum01.fs

@@ -0,0 +1,26 @@
+open System
+
+[<AttributeUsage(AttributeTargets.Struct)>]
+type CustomStructAttribute() =
+    inherit Attribute()
+
+[<AttributeUsage(AttributeTargets.Class)>]
+type CustomClassAttribute() =
+    inherit Attribute()
+
+[<AttributeUsage(AttributeTargets.Interface)>]
+type CustomInterfaceAttribute() =
+    inherit Attribute()
+
+[<AttributeUsage(AttributeTargets.Delegate)>]
+type CustomDelegateAttribute() =
+    inherit Attribute()
+
+[<CustomStruct>]
+[<CustomClass>]
+[<CustomInterface>]
+[<CustomDelegate>]
+type Color =
+    | Red = 0
+    | Green = 1
+    | Blue = 2