Delegates allowed to target AttributeTargets.Class AttributeTargets.Struct AttributeTargets.Interface incorrectly

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

@@ -21,6 +21,7 @@
 * 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))
+* Enforce AttributeTargets on delegates ([PR #16891](https://github.com/dotnet/fsharp/pull/16891))
 
 ### Added
 

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

@@ -7,4 +7,5 @@
 
 * 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 enums. Also update `RequireQualifiedAccessAttribute` to use `AttributeTargets.Enum` ([PR #16887](https://github.com/dotnet/fsharp/pull/16887))
+* Enforce AttributeTargets on enums. Also update `RequireQualifiedAccessAttribute` to use `AttributeTargets.Enum` ([PR #16887](https://github.com/dotnet/fsharp/pull/16887))
+* Enforce AttributeTargets on delegates. Also update `ReflectedDefinitionAttribute` to use `AttributeTargets.Delegate` ([PR #16891](https://github.com/dotnet/fsharp/pull/16891))

src/Compiler/Checking/CheckDeclarations.fs

@@ -2931,7 +2931,10 @@ module EstablishTypeDefinitionCores =
                                 TcAttributesWithPossibleTargets false cenv envinner AttributeTargets.Class synAttrs |> ignore
                             TFSharpClass
                         | SynTypeDefnKind.Interface -> TFSharpInterface
-                        | SynTypeDefnKind.Delegate _ -> TFSharpDelegate (MakeSlotSig("Invoke", g.unit_ty, [], [], [], None))
+                        | SynTypeDefnKind.Delegate _ ->
+                            if g.langVersion.SupportsFeature(LanguageFeature.EnforceAttributeTargets) then
+                                TcAttributesWithPossibleTargets false cenv envinner AttributeTargets.Delegate synAttrs |> ignore
+                            TFSharpDelegate (MakeSlotSig("Invoke", g.unit_ty, [], [], [], None))
                         | SynTypeDefnKind.Struct ->
                             if g.langVersion.SupportsFeature(LanguageFeature.EnforceAttributeTargets) then
                                 TcAttributesWithPossibleTargets false cenv envinner AttributeTargets.Struct synAttrs |> ignore

src/FSharp.Core/prim-types.fs

@@ -163,7 +163,8 @@ namespace Microsoft.FSharp.Core
 
     [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct |||
                       AttributeTargets.Parameter ||| AttributeTargets.Method |||
-                      AttributeTargets.Property ||| AttributeTargets.Constructor, AllowMultiple=false)>]  
+                      AttributeTargets.Property ||| AttributeTargets.Constructor |||
+                      AttributeTargets.Delegate, AllowMultiple=false)>]  
     [<Sealed>]
     type ReflectedDefinitionAttribute(includeValue: bool) =
         inherit Attribute()

src/FSharp.Core/prim-types.fsi

@@ -129,7 +129,7 @@ namespace Microsoft.FSharp.Core
     /// for use at runtime.</summary>
     ///
     /// <category>Attributes</category>
-    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct ||| AttributeTargets.Parameter ||| AttributeTargets.Method ||| AttributeTargets.Property ||| AttributeTargets.Constructor,AllowMultiple=false)>]  
+    [<AttributeUsage (AttributeTargets.Class ||| AttributeTargets.Struct ||| AttributeTargets.Parameter ||| AttributeTargets.Method ||| AttributeTargets.Property ||| AttributeTargets.Constructor ||| AttributeTargets.Delegate, AllowMultiple=false)>]  
     [<Sealed>]
     type ReflectedDefinitionAttribute =
         inherit Attribute

tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/CustomAttributes/AttributeUsage/AttributeTargetsIsDelegate01.fs

@@ -0,0 +1,8 @@
+open System
+
+[<AttributeUsage(AttributeTargets.Delegate)>]
+type CustomDelegateAttribute() =
+    inherit Attribute()
+
+[<CustomDelegate>]
+type Delegate1 = delegate of int -> int

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

@@ -555,4 +555,40 @@ module CustomAttributes_AttributeUsage =
             (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")
+        ]
+
+     // SOURCE=AttributeTargetsIsDelegate01.fs	# AttributeTargetsIsDelegate01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"AttributeTargetsIsDelegate01.fs"|])>]
+    let ``AttributeTargetsIsDelegate01_fs`` compilation =
+        compilation
+        |> verifyCompile
+        |> shouldSucceed
+
+    // SOURCE=AttributeTargetsIsDelegate01.fs	# AttributeTargetsIsDelegate01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"AttributeTargetsIsDelegate01.fs"|])>]
+    let ``AttributeTargetsIsDelegate01_fs preview`` compilation =
+        compilation
+        |> withLangVersionPreview
+        |> verifyCompile
+        |> shouldSucceed
+
+    // SOURCE=E_AttributeTargetIsDelegate01.fs	# E_AttributeTargetIsDelegate01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"E_AttributeTargetIsDelegate01.fs"|])>]
+    let ``E_AttributeTargetIsDelegate01_fs`` compilation =
+        compilation
+        |> verifyCompile
+        |> shouldSucceed
+
+    // SOURCE=E_AttributeTargetIsDelegate01.fs	# E_AttributeTargetIsDelegate01.fs
+    [<Theory; Directory(__SOURCE_DIRECTORY__, Includes=[|"E_AttributeTargetIsDelegate01.fs"|])>]
+    let ``E_AttributeTargetsIsDelegate01_fs preview`` compilation =
+        compilation
+        |> withLangVersionPreview
+        |> verifyCompile
+        |> shouldFail
+        |> withDiagnostics [
+            (Error 842, Line 19, Col 3, Line 19, Col 14, "This attribute is not valid for use on this language element")
+            (Error 842, Line 20, Col 3, Line 20, Col 15, "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 13, "This attribute is not valid for use on this language element")
         ]

tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/CustomAttributes/AttributeUsage/E_AttributeTargetIsDelegate01.fs

@@ -0,0 +1,23 @@
+open System
+
+[<AttributeUsage(AttributeTargets.Class)>]
+type CustomClassAttribute() =
+    inherit Attribute()
+
+[<AttributeUsage(AttributeTargets.Struct)>]
+type CustomStructAttribute() =
+    inherit Attribute()
+
+[<AttributeUsage(AttributeTargets.Interface)>]
+type CustomInterfaceAttribute() =
+    inherit Attribute()
+
+[<AttributeUsage(AttributeTargets.Enum)>]
+type CustomEnumAttribute() =
+    inherit Attribute()
+
+[<CustomClass>]
+[<CustomStruct>]
+[<CustomInterface>]
+[<CustomEnum>]
+type Delegate1 = delegate of int -> int