Compiler error when implementing interfaces on static classes

src/Compiler/Checking/CheckDeclarations.fs

@@ -1668,6 +1668,8 @@ let private ReportErrorOnStaticClass (synMembers: SynMemberDefn list) =
             errorR(Error(FSComp.SR.chkInstanceMemberOnStaticClasses(), m))
         | SynMemberDefn.LetBindings(isStatic = false; range = range) ->
             errorR(Error(FSComp.SR.chkInstanceLetBindingOnStaticClasses(), range))
+        | SynMemberDefn.Interface(range = range) ->
+            errorR(Error(FSComp.SR.chkImplementingInterfacesOnStaticClasses(), range))
         | _ -> ()
 
 /// Check and generalize the interface implementations, members, 'let' definitions in a mutually recursive group of definitions.

src/Compiler/FSComp.txt

@@ -1669,4 +1669,5 @@ featureEscapeBracesInFormattableString,"Escapes curly braces before calling Form
 3552,chkConstructorWithArgumentsOnStaticClasses,"If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Constructor with arguments is not allowed."
 3553,chkAdditionalConstructorOnStaticClasses,"If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Additional constructor is not allowed."
 3554,chkInstanceMemberOnStaticClasses,"If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Instance members are not allowed."
-3555,chkInstanceLetBindingOnStaticClasses,"If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Instance let bindings are not allowed."
+3555,chkInstanceLetBindingOnStaticClasses,"If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Instance let bindings are not allowed."
+3556,chkImplementingInterfacesOnStaticClasses,"If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Implementing interfaces is not allowed."

src/Compiler/xlf/FSComp.txt.cs.xlf

@@ -52,6 +52,11 @@
         <target state="translated">Funkce {0} vyžaduje knihovnu F# pro verzi jazyka {1} nebo novější.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">Použití := z knihovny F# je zastaralé. Více informací: https://aka.ms/fsharp-refcell-ops. Změňte prosím například cell := expr na cell.Value &lt;- expr.</target>

src/Compiler/xlf/FSComp.txt.de.xlf

@@ -52,6 +52,11 @@
         <target state="translated">Für das Feature "{0}" ist die F#-Bibliothek für die Sprachversion {1} oder höher erforderlich.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">Die Verwendung von ":=" aus der F#-Bibliothek ist veraltet. Siehe https://aka.ms/fsharp-refcell-ops. Ändern Sie z. B. "cell := expr" in "cell.Value &lt;- expr".</target>

src/Compiler/xlf/FSComp.txt.es.xlf

@@ -52,6 +52,11 @@
         <target state="translated">La característica "{0}" requiere la biblioteca de F# para la versión de lenguaje {1} o superior.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">El uso de ":=" de la biblioteca de F# está en desuso. Vea https://aka.ms/fsharp-refcell-ops. Por ejemplo, cambie "cell := expr" a "cell.Value &lt;- expr".</target>

src/Compiler/xlf/FSComp.txt.fr.xlf

@@ -52,6 +52,11 @@
         <target state="translated">La fonctionnalité '{0}' nécessite la bibliothèque F# pour le langage version {1} ou ultérieure.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">L’utilisation de « := » à partir de la bibliothèque F# est déconseillée. Voir https://aka.ms/fsharp-refcell-ops. Par exemple, veuillez remplacer « cell := expr » par « cell.Value &lt;- expr ».</target>

src/Compiler/xlf/FSComp.txt.it.xlf

@@ -52,6 +52,11 @@
         <target state="translated">Con la funzionalità '{0}' è richiesta la libreria F# per la versione {1} o successiva del linguaggio.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">L'uso di ':=' dalla libreria F # è deprecato. Vedere https://aka.ms/fsharp-refcell-ops. Ad esempio, modificare 'cell:= expr' in 'cell.Value &lt;- expr'.</target>

src/Compiler/xlf/FSComp.txt.ja.xlf

@@ -52,6 +52,11 @@
         <target state="translated">機能 '{0}' を使用するには、言語バージョン {1} 以上の F# ライブラリが必要です。</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">F# ライブラリからの ':=' の使用は非推奨です。https://aka.ms/fsharp-refcell-ops を参照してください。たとえば、'cell : = expr' を 'cell.Value &lt;- expr' に変更してください。</target>

src/Compiler/xlf/FSComp.txt.ko.xlf

@@ -52,6 +52,11 @@
         <target state="translated">언어 버전 {1} 이상에서 '{0}' 기능을 사용하려면 F# 라이브러리가 필요합니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">F# 라이브러리의 ':=' 사용은 더 이상 사용되지 않습니다. https://aka.ms/fsharp-refcell-ops를 참조하세요. 예를 들어 'cell := expr'을 'cell.Value &lt;- expr'로 변경하세요.</target>

src/Compiler/xlf/FSComp.txt.pl.xlf

@@ -52,6 +52,11 @@
         <target state="translated">Funkcja „{0}” wymaga biblioteki języka F# dla wersji językowej {1} lub nowszej.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">Użycie elementu „:=” z biblioteki języka F# jest przestarzałe. Sprawdź stronę https://aka.ms/fsharp-refcell-ops. Na przykład zmień wyrażenie „cell := expr” na „cell.Value &lt;- expr”.</target>

src/Compiler/xlf/FSComp.txt.pt-BR.xlf

@@ -52,6 +52,11 @@
         <target state="translated">O recurso '{0}' exige a biblioteca F# para a versão da linguagem {1} ou posterior.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">O uso de ':=' da biblioteca F# foi preterido. Consulte https://aka.ms/fsharp-refcell-ops. Por exemplo, altere 'cell := expr' para 'cell.Value &lt;- expr'.</target>

src/Compiler/xlf/FSComp.txt.ru.xlf

@@ -52,6 +52,11 @@
         <target state="translated">Компоненту "{0}" требуется библиотека F# для языка версии {1} или более поздней.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">Использование ":=" из библиотеки F# является нерекомендуемым. См. https://aka.ms/fsharp-refcell-ops. Например, замените "cell := expr" на "cell.Value &lt;- expr".</target>

src/Compiler/xlf/FSComp.txt.tr.xlf

@@ -52,6 +52,11 @@
         <target state="translated">'{0}' özelliği için F# kitaplığının {1} veya üstü dil sürümü gerekir.</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">F# kitaplığından gelen ':=' kullanımı kullanım dışı. https://aka.ms/fsharp-refcell-ops’a bakın. Örneğin, lütfen 'cell := expr' ifadesini 'cell.Value &lt;- expr' olarak değiştirin.</target>

src/Compiler/xlf/FSComp.txt.zh-Hans.xlf

@@ -52,6 +52,11 @@
         <target state="translated">功能“{0}”需要 {1} 或更高语言版本的 F# 库。</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">已弃用 F# 库中的“:=”。请参阅 https://aka.ms/fsharp-refcell-ops。 例如，请将“cell := expr”更改为“cell.Value &lt;- expr”。</target>

src/Compiler/xlf/FSComp.txt.zh-Hant.xlf

@@ -52,6 +52,11 @@
         <target state="translated">功能 '{0}' 需要語言版本 {1} 或更高的 F# 程式庫。</target>
         <note />
       </trans-unit>
+      <trans-unit id="chkImplementingInterfacesOnStaticClasses">
+        <source>If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</source>
+        <target state="new">If a type uses both [&lt;Sealed&gt;] and [&lt;AbstractClass&gt;] attributes, it means it is static. Implementing interfaces is not allowed.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="chkInfoRefcellAssign">
         <source>The use of ':=' from the F# library is deprecated. See https://aka.ms/fsharp-refcell-ops. For example, please change 'cell := expr' to 'cell.Value &lt;- expr'.</source>
         <target state="translated">透過 F# 程式庫使用 ':=' 的方式已淘汰。請參閱 https://aka.ms/fsharp-refcell-ops。舉例來說，請將 'cell := expr' 變更為 'cell.Value &lt;- expr'。</target>

tests/FSharp.Compiler.ComponentTests/Language/StaticClassTests.fs

@@ -354,4 +354,70 @@ type C() =
         """
          |> withLangVersionPreview
          |> compile
-         |> shouldSucceed
+         |> shouldSucceed
+
+    [<Fact>]
+    let ``Sealed and AbstractClass on a type implementing interface in lang 70`` () =
+        Fsx """
+type MyInterface =
+    abstract member M : unit -> unit
+
+[<Sealed; AbstractClass>]
+type C() =
+    interface MyInterface with
+        member this.M() = ()
+        """
+         |> withLangVersion70
+         |> compile
+         |> shouldSucceed
+
+    [<Fact>]
+    let ``Sealed and AbstractClass on a type implicit constructor implementing interface in lang 70`` () =
+        Fsx """
+type MyInterface =
+    abstract member M : unit -> unit
+
+[<Sealed; AbstractClass>]
+type C =
+    interface MyInterface with
+        member this.M() = ()
+        """
+         |> withLangVersion70
+         |> compile
+         |> shouldSucceed
+
+    [<Fact>]
+    let ``Sealed and AbstractClass on a type implementing interface in lang preview`` () =
+        Fsx """
+type MyInterface =
+    abstract member M : unit -> unit
+
+[<Sealed; AbstractClass>]
+type C() =
+    interface MyInterface with
+        member this.M() = ()
+        """
+         |> withLangVersionPreview
+         |> compile
+         |> shouldFail
+         |> withDiagnostics [
+            (Error 3556, Line 7, Col 5, Line 8, Col 29, "If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Implementing interfaces is not allowed.")
+         ]
+
+    [<Fact>]
+    let ``Sealed and AbstractClass on a type implicit constructor implementing interface in lang preview`` () =
+        Fsx """
+type MyInterface =
+    abstract member M : unit -> unit
+
+[<Sealed; AbstractClass>]
+type C =
+    interface MyInterface with
+        member this.M() = ()
+        """
+         |> withLangVersionPreview
+         |> compile
+         |> shouldFail
+         |> withDiagnostics [
+            (Error 3556, Line 7, Col 5, Line 8, Col 29, "If a type uses both [<Sealed>] and [<AbstractClass>] attributes, it means it is static. Implementing interfaces is not allowed.")
+         ]