Allow interfaces to be declared and implemented within intrinsics (#11170)

* Changing warning to implementing interfaces within intrisincs
* In case of recursive namespaces and modules, warning is not generated
* Adding tests for combinations of rec and non-rec modules/namespaces/nested namespaces

src/Compiler/Checking/CheckDeclarations.fs

@@ -1636,7 +1636,7 @@ module MutRecBindingChecking =
         defnsEs, envMutRec
 
 /// Check and generalize the interface implementations, members, 'let' definitions in a mutually recursive group of definitions.
-let TcMutRecDefns_Phase2 (cenv: cenv) envInitial mBinds scopem mutRecNSInfo (envMutRec: TcEnv) (mutRecDefns: MutRecDefnsPhase2Data) = 
+let TcMutRecDefns_Phase2 (cenv: cenv) envInitial mBinds scopem mutRecNSInfo (envMutRec: TcEnv) (mutRecDefns: MutRecDefnsPhase2Data) isMutRec =     
     let g = cenv.g
     let interfacesFromTypeDefn envForTycon tyconMembersData = 
         let (MutRecDefnsPhase2DataForTycon(_, _, declKind, tcref, _, _, declaredTyconTypars, members, _, _, _)) = tyconMembersData
@@ -1665,11 +1665,13 @@ let TcMutRecDefns_Phase2 (cenv: cenv) envInitial mBinds scopem mutRecNSInfo (env
                       (generatedHashAndEqualsWithComparerValues && typeEquiv g intfTyR (mkAppTy g.system_GenericIEquatable_tcref [ty])) ||
                       (generatedHashAndEqualsWithComparerValues && typeEquiv g intfTyR g.mk_IStructuralEquatable_ty) then
                       errorR(Error(FSComp.SR.tcDefaultImplementationForInterfaceHasAlreadyBeenAdded(), intfTy.Range))
-
-                  if overridesOK = WarnOnOverrides then  
-                      warning(IntfImplInIntrinsicAugmentation(intfTy.Range))
-                  if overridesOK = ErrorOnOverrides then  
-                      errorR(IntfImplInExtrinsicAugmentation(intfTy.Range))
+           
+                  match isMutRec, overridesOK with
+                  | _, OverridesOK  -> () // No warning/error if overrides are allowed
+                  | true, WarnOnOverrides -> () // If we are in a recursive module/namespace, overrides of interface implementations are allowed and not considered a warning
+                  | false, WarnOnOverrides -> warning(IntfImplInIntrinsicAugmentation(intfTy.Range))
+                  | _, ErrorOnOverrides -> errorR(IntfImplInExtrinsicAugmentation(intfTy.Range))
+                
                   match defnOpt with 
                   | Some defn -> [ (intfTyR, defn, m) ]
                   | _-> []
@@ -2270,7 +2272,7 @@ module TcExceptionDeclarations =
         let envMutRec = AddLocalExnDefnAndReport cenv.tcSink scopem (AddLocalTycons g cenv.amap scopem [exnc] envInitial) exnc 
 
         let defns = [MutRecShape.Tycon(MutRecDefnsPhase2DataForTycon(Some exnc, parent, ModuleOrMemberBinding, mkLocalEntityRef exnc, None, NoSafeInitInfo, [], aug, m, NoNewSlots, (fun () -> ())))]
-        let binds2, envFinal = TcMutRecDefns_Phase2 cenv envInitial m scopem None envMutRec defns
+        let binds2, envFinal = TcMutRecDefns_Phase2 cenv envInitial m scopem None envMutRec defns true
         let binds2flat = binds2 |> MutRecShapes.collectTycons |> List.collect snd
         // Augment types with references to values that implement the pre-baked semantics of the type
         let binds3 = AddAugmentationDeclarations.AddGenericEqualityBindings cenv envFinal exnc
@@ -4162,7 +4164,7 @@ module TcDeclarations =
     //-------------------------------------------------------------------------
 
     /// Bind a collection of mutually recursive definitions in an implementation file
-    let TcMutRecDefinitions (cenv: cenv) envInitial parent typeNames tpenv m scopem mutRecNSInfo (mutRecDefns: MutRecDefnsInitialData) =
+    let TcMutRecDefinitions (cenv: cenv) envInitial parent typeNames tpenv m scopem mutRecNSInfo (mutRecDefns: MutRecDefnsInitialData) isMutRec =
 
         let g = cenv.g
 
@@ -4216,7 +4218,7 @@ module TcDeclarations =
                        cenv true scopem m 
 
         // Check the members and decide on representations for types with implicit constructors.
-        let withBindings, envFinal = TcMutRecDefns_Phase2 cenv envInitial m scopem mutRecNSInfo envMutRecPrelimWithReprs withEnvs
+        let withBindings, envFinal = TcMutRecDefns_Phase2 cenv envInitial m scopem mutRecNSInfo envMutRecPrelimWithReprs withEnvs isMutRec
 
         // Generate the hash/compare/equality bindings for all tycons.
         //
@@ -4674,7 +4676,7 @@ let rec TcModuleOrNamespaceElementNonMutRec (cenv: cenv) parent typeNames scopem
       | SynModuleDecl.Types (typeDefs, m) -> 
           let scopem = unionRanges m scopem
           let mutRecDefns = typeDefs |> List.map MutRecShape.Tycon
-          let mutRecDefnsChecked, envAfter = TcDeclarations.TcMutRecDefinitions cenv env parent typeNames tpenv m scopem None mutRecDefns
+          let mutRecDefnsChecked, envAfter = TcDeclarations.TcMutRecDefinitions cenv env parent typeNames tpenv m scopem None mutRecDefns false
           // Check the non-escaping condition as we build the expression on the way back up 
           let defn = TcMutRecDefsFinish cenv mutRecDefnsChecked m
           let escapeCheck () = 
@@ -4725,7 +4727,7 @@ let rec TcModuleOrNamespaceElementNonMutRec (cenv: cenv) parent typeNames scopem
           // Treat 'module rec M = ...' as a single mutually recursive definition group 'module M = ...'
           if isRec then 
               assert (not isContinuingModule)
-              let modDecl = SynModuleDecl.NestedModule(compInfo, false, moduleDefs, isContinuingModule, m, trivia)
+              let modDecl = SynModuleDecl.NestedModule(compInfo, false, moduleDefs, isContinuingModule, m, trivia)            
               return! TcModuleOrNamespaceElementsMutRec cenv parent typeNames m env None [modDecl]
           else
               let (SynComponentInfo(Attributes attribs, _, _, longPath, xml, _, vis, im)) = compInfo
@@ -4927,7 +4929,7 @@ and TcModuleOrNamespaceElementsMutRec (cenv: cenv) parent typeNames m envInitial
       loop (match parent with ParentNone -> true | Parent _ -> false) m [] defs
 
     let tpenv = emptyUnscopedTyparEnv 
-    let mutRecDefnsChecked, envAfter = TcDeclarations.TcMutRecDefinitions cenv envInitial parent typeNames tpenv m scopem mutRecNSInfo mutRecDefns 
+    let mutRecDefnsChecked, envAfter = TcDeclarations.TcMutRecDefinitions cenv envInitial parent typeNames tpenv m scopem mutRecNSInfo mutRecDefns true
 
     // Check the assembly attributes
     let attrs, _ = TcAttributesWithPossibleTargets false cenv envAfter AttributeTargets.Top synAttrs

src/Compiler/FSStrings.resx

@@ -1054,7 +1054,7 @@
     <value>Override implementations should be given as part of the initial declaration of a type.</value>
   </data>
   <data name="IntfImplInIntrinsicAugmentation" xml:space="preserve">
-    <value>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</value>
+    <value>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</value>
   </data>
   <data name="IntfImplInExtrinsicAugmentation" xml:space="preserve">
     <value>Interface implementations should be given on the initial declaration of a type.</value>

src/Compiler/xlf/FSStrings.cs.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Implementace rozhraní v rozšířeních jsou už zastaralé. Implementace rozhraní by se měly provádět při počáteční deklaraci typu.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Implementace rozhraní v rozšířeních jsou už zastaralé. Implementace rozhraní by se měly provádět při počáteční deklaraci typu.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.de.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Schnittstellenimplementierungen in Augmentationen sind jetzt veraltet. Schnittstellenimplementierungen sollten in der ersten Deklaration eines Typs angegeben werden.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Schnittstellenimplementierungen in Augmentationen sind jetzt veraltet. Schnittstellenimplementierungen sollten in der ersten Deklaration eines Typs angegeben werden.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.es.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Las implementaciones de interfaz en aumentos están en desuso. Las implementaciones de interfaz deben proporcionarse en la declaración inicial de un tipo.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Las implementaciones de interfaz en aumentos están en desuso. Las implementaciones de interfaz deben proporcionarse en la declaración inicial de un tipo.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.fr.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Les implémentations d'interfaces dans les augmentations sont désormais déconseillées. Les implémentations d'interfaces doivent être fournies dans la déclaration initiale d'un type.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Les implémentations d'interfaces dans les augmentations sont désormais déconseillées. Les implémentations d'interfaces doivent être fournies dans la déclaration initiale d'un type.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.it.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Le implementazioni di interfaccia negli aumenti sono ora deprecate. Le implementazioni di interfaccia devono essere specificate nella dichiarazione iniziale di un tipo.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Le implementazioni di interfaccia negli aumenti sono ora deprecate. Le implementazioni di interfaccia devono essere specificate nella dichiarazione iniziale di un tipo.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.ja.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">拡張内のインターフェイスの実装は使用されなくなりました。インターフェイスの実装は、型の最初の宣言で指定してください。</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">拡張内のインターフェイスの実装は使用されなくなりました。インターフェイスの実装は、型の最初の宣言で指定してください。</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.ko.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">확대의 인터페이스 구현은 이제 사용되지 않습니다. 인터페이스 구현은 초기 형식 선언 시 지정해야 합니다.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">확대의 인터페이스 구현은 이제 사용되지 않습니다. 인터페이스 구현은 초기 형식 선언 시 지정해야 합니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.pl.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Implementacje interfejsów w powiększeniach są teraz przestarzałe. Implementacje interfejsów powinny występować w początkowej deklaracji typu.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Implementacje interfejsów w powiększeniach są teraz przestarzałe. Implementacje interfejsów powinny występować w początkowej deklaracji typu.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.pt-BR.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Implementações de interface em aumentos agora são preteridas. Implementações de interface devem ser dadas nas declarações de tipo iniciais.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Implementações de interface em aumentos agora são preteridas. Implementações de interface devem ser dadas nas declarações de tipo iniciais.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.ru.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Реализации интерфейсов в приращениях теперь являются не рекомендуемыми к использованию. Реализации интерфейсов должны быть даны при первичном объявлении типа.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Реализации интерфейсов в приращениях теперь являются не рекомендуемыми к использованию. Реализации интерфейсов должны быть даны при первичном объявлении типа.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.tr.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">Genişletmelerdeki arabirim uygulamaları artık kullanım dışı bırakıldı. Arabirim uygulamaları bir türün ilk bildiriminde verilmelidir.</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">Genişletmelerdeki arabirim uygulamaları artık kullanım dışı bırakıldı. Arabirim uygulamaları bir türün ilk bildiriminde verilmelidir.</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.zh-Hans.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">扩大中的接口实现现已弃用。应在类型的初始声明中提供接口实现。</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">扩大中的接口实现现已弃用。应在类型的初始声明中提供接口实现。</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/Compiler/xlf/FSStrings.zh-Hant.xlf

@@ -1558,8 +1558,8 @@
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInIntrinsicAugmentation">
-        <source>Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.</source>
-        <target state="translated">增強指定中的介面實作現在已被取代。應該在類型的初始宣告上指定介面實作。</target>
+        <source>Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.</source>
+        <target state="needs-review-translation">增強指定中的介面實作現在已被取代。應該在類型的初始宣告上指定介面實作。</target>
         <note />
       </trans-unit>
       <trans-unit id="IntfImplInExtrinsicAugmentation">

src/FSharp.Core/prim-types.fs

@@ -6,7 +6,7 @@
 #nowarn "52" // The value has been copied to ensure the original is not mutated by this operation
 #nowarn "60" // Override implementations in augmentations are now deprecated. Override implementations should be given as part of the initial declaration of a type.
 #nowarn "61" // The containing type can use 'null' as a representation value for its nullary union case. This member will be compiled as a static member.
-#nowarn "69" // Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration...
+#nowarn "69" // Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.
 #nowarn "77" // Member constraints with the name 'Exp' are given special status by the F# compiler...
 #nowarn "3218" // mismatch of parameter name for 'fst' and 'snd'
 

tests/FSharp.Compiler.ComponentTests/ErrorMessages/InterfaceImplInAugmentationsTests.fs

+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.ComponentTests.ErrorMessages
+
+open Xunit
+open FSharp.Test.Compiler
+
+
+module InterfaceImplAugmentation =
+    [<Fact>]
+    let ``Type in non-recursive namespace gives a warning when augmented externally``() =
+        FSharp """
+namespace AugmentationsTest
+type MyCustomType<'T> = 
+    | Data of string
+    interface System.IDisposable
+
+type MyCustomType<'T> with
+    interface System.IDisposable with
+                member x.Dispose() = printfn "Finish"   """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 69, Line 8, Col 15, Line 8, Col 33,
+                                 """Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.""")
+
+    [<Fact>]
+    let ``Exception type in non-recursive namespace gives a warning when augmented externally``() =
+        FSharp """
+namespace AugmentationsTest
+type MyCustomExcType<'T>() = 
+    inherit System.Exception()   
+    interface System.IDisposable
+
+type MyCustomExcType<'T> with
+    interface System.IDisposable with
+                member x.Dispose() = printfn "Finish"   """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 69, Line 8, Col 15, Line 8, Col 33,
+                                 """Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.""")
+
+
+    [<Fact>]
+    let ``Type in a recursive namespace can be augmented without warning``() =
+        FSharp """
+namespace rec AugmentationsTest
+type MyCustomType<'T> = 
+    | Data of string
+    interface System.IDisposable
+
+type MyCustomType<'T> with
+    interface System.IDisposable with
+                member x.Dispose() = printfn "Finish"   """
+        |> typecheck
+        |> shouldSucceed
+        |> withWarnings []
+
+    [<Fact>]
+    let ``Exception in a recursive namespace can be augmented without warning``() =
+        FSharp """
+namespace rec AugmentationsTest
+type MyCustomExcType<'T>() = 
+    inherit System.Exception()   
+    interface System.IDisposable
+
+type MyCustomExcType<'T> with
+    interface System.IDisposable with
+                member x.Dispose() = printfn "Finish"    """
+        |> typecheck
+        |> shouldSucceed
+        |> withWarnings []
+
+    [<Fact>]
+    let ``Type in a recursive module and in a non-recursive namespace can be augmented without warning``() =
+        FSharp """
+namespace MyNonRecursiveNs
+module rec RecursiveModule = 
+    type MyCustomType<'T> = 
+        | Data of string
+        interface System.IDisposable
+
+    type MyCustomType<'T> with
+        interface System.IDisposable with
+                    member x.Dispose() = printfn "Finish"   """
+        |> typecheck
+        |> shouldSucceed
+        |> withWarnings []
+
+    [<Fact>]
+    let ``Type in a nonrecursive module but in a recursive namespace can be augmented without warning``() =
+        FSharp """
+namespace rec AugmentationsTest
+module InnerNonRecursiveModule = 
+    type MyCustomType<'T> = 
+        | Data of string
+        interface System.IDisposable
+
+    type MyCustomType<'T> with
+        interface System.IDisposable with
+                    member x.Dispose() = printfn "Finish"   """
+        |> typecheck
+        |> shouldSucceed
+        |> withWarnings []
+
+    [<Fact>]
+    let ``Type in non-recursive namespace nested in a bigger recursive namespace shows warning``() =
+        FSharp """
+namespace rec OuuterRec
+namespace OuuterRec.InnerNonRec
+    type MyCustomType<'T> = 
+        | Data of string
+        interface System.IDisposable
+
+    type MyCustomType<'T> with
+        interface System.IDisposable with
+                    member x.Dispose() = printfn "Finish"     """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 69, Line 9, Col 19, Line 9, Col 37,
+                                 """Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.""")
+
+ 
+   
+    [<Fact>]
+    let ``Type in non-rec ns show give a warning when augmented externally even when the same file has a recursive (but different) ns``() =
+        FSharp """
+namespace rec OuuterRec
+    module Stuff = 
+        let x = 5
+namespace TotallyDifferentNs.InnerNonRec
+    type MyCustomType<'T> = 
+        | Data of string
+        interface System.IDisposable
+
+    type MyCustomType<'T> with
+        interface System.IDisposable with
+                    member x.Dispose() = printfn "Finish"    """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 69, Line 11, Col 19, Line 11, Col 37,
+                                 """Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.""")
+
+    [<Fact>]
+    let ``Adding an interface to a previously defined type should still be just an 909 error and nothing else``() =
+        FSharp """
+type System.Random with
+    interface System.IComparable 
+    static member Factory() = 1     """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Error 909, Line 3, Col 15, Line 3, Col 33,
+                                 """All implemented interfaces should be declared on the initial declaration of the type""")
+
+ 
\ No newline at end of file

tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj

@@ -134,7 +134,7 @@
     <Compile Include="EmittedIL\Structure\Structure.fs" />
     <Compile Include="EmittedIL\TestFunctions\TestFunctions.fs" />
     <Compile Include="EmittedIL\Tuples\Tuples.fs" />
-	<Compile Include="EmittedIL\StructDefensiveCopy\StructDefensiveCopy.fs" />
+    <Compile Include="EmittedIL\StructDefensiveCopy\StructDefensiveCopy.fs" />
     <Compile Include="ErrorMessages\UnsupportedAttributes.fs" />
     <Compile Include="ErrorMessages\TypeEqualsMissingTests.fs" />
     <Compile Include="ErrorMessages\AccessOfTypeAbbreviationTests.fs" />
@@ -159,9 +159,10 @@
     <Compile Include="ErrorMessages\FS0988AtEndOfFile.fs" />
     <Compile Include="ErrorMessages\Repro1548.fs" />
     <Compile Include="ErrorMessages\WarnIfDiscardedInList.fs" />
-	<Compile Include="ErrorMessages\UnionCasePatternMatchingErrors.fs"/>
+    <Compile Include="ErrorMessages\UnionCasePatternMatchingErrors.fs"/>
+    <Compile Include="ErrorMessages\InterfaceImplInAugmentationsTests.fs"/>	
     <Compile Include="Language\IndexerSetterParamArray.fs" />
-	<Compile Include="Language\MultiDimensionalArrayTests.fs" />
+    <Compile Include="Language\MultiDimensionalArrayTests.fs" />
     <Compile Include="Language\RegressionTests.fs" />
     <Compile Include="Language\AttributeCheckingTests.fs" />
     <Compile Include="Language\ObsoleteAttributeCheckingTests.fs" />
@@ -181,8 +182,8 @@
       <Link>%(RelativeDir)\TestSource\%(Filename)%(Extension)</Link>
     </None>
     <Compile Include="Interop\SimpleInteropTests.fs" />
-	<Compile Include="Interop\RequiredAndInitOnlyProperties.fs" />
-	<Compile Include="Interop\StaticsInInterfaces.fs" />
+    <Compile Include="Interop\RequiredAndInitOnlyProperties.fs" />
+    <Compile Include="Interop\StaticsInInterfaces.fs" />
     <Compile Include="Interop\VisibilityTests.fs" />
     <Compile Include="Scripting\Interactive.fs" />
     <Compile Include="TypeChecks\CheckDeclarationsTests.fs" />

tests/fsharp/typecheck/sigs/neg10.bsl

@@ -29,7 +29,7 @@ neg10.fs(25,16,25,53): typecheck error FS0001: This type parameter cannot be ins
 
 neg10.fs(54,17,54,20): typecheck error FS0060: Override implementations in augmentations are now deprecated. Override implementations should be given as part of the initial declaration of a type.
 
-neg10.fs(66,19,66,21): typecheck error FS0069: Interface implementations in augmentations are now deprecated. Interface implementations should be given on the initial declaration of a type.
+neg10.fs(66,19,66,21): typecheck error FS0069: Interface implementations should normally be given on the initial declaration of a type. Interface implementations in augmentations may lead to accessing static bindings before they are initialized, though only if the interface implementation is invoked during initialization of the static data, and in turn access the static data. You may remove this warning using #nowarn "69" if you have checked this is not the case.
 
 neg10.fs(77,13,77,34): typecheck error FS0896: Enumerations cannot have members
 

tests/fsharp/typecheck/sigs/neg46.bsl

@@ -37,4 +37,4 @@ neg46.fs(64,8,64,26): typecheck error FS0912: This declaration element is not pe
 
 neg46.fs(68,18,68,36): typecheck error FS0909: All implemented interfaces should be declared on the initial declaration of the type
 
-neg46.fs(73,18,73,36): typecheck error FS0909: All implemented interfaces should be declared on the initial declaration of the type
+neg46.fs(73,18,73,36): typecheck error FS0909: All implemented interfaces should be declared on the initial declaration of the type
\ No newline at end of file

tests/fsharpqa/Source/Conformance/ObjectOrientedTypeDefinitions/TypeExtensions/intrinsic/env.lst

@@ -2,5 +2,4 @@
 	SOURCE="lib002.fs E_typeext_int002.fs" SCFLAGS="--test:ErrorRanges"	# E_typeext_int002.fs
 	SOURCE="lib003.fs typeext_int003.fs"					# typeext_int003.fs
     	SOURCE="lib004.fs typeext_int004.fs"					# typeext_int004fs
-    	SOURCE="lib005.fs typeext_int005.fs"					# typeext_int005fs
-    	SOURCE="lib006.fs typeext_int006.fs" SCFLAGS="--test:ErrorRanges"	# typeext_int006.fs
+    	SOURCE="lib005.fs typeext_int005.fs"					# typeext_int005fs
\ No newline at end of file

tests/fsharpqa/Source/Conformance/ObjectOrientedTypeDefinitions/TypeExtensions/intrinsic/lib006.fs

-// #Regression #Conformance #ObjectOrientedTypes #TypeExtensions 
-//<Expects id="FS0909" span="(7,17-7,19)" status="error">All implemented interfaces should be declared on the initial declaration of the type</Expects>
-
-namespace NS
-    type IM = 
-      interface
-        abstract M : int -> int
-      end
-      
-    type Lib() =
-      class
-          member x.Prop = 1
-     end
- 

tests/fsharpqa/Source/Conformance/ObjectOrientedTypeDefinitions/TypeExtensions/intrinsic/typeext_int006.fs

-// #Conformance #ObjectOrientedTypes #TypeExtensions 
-// verify that implementing an interface is not allowed 
-
-namespace NS
-  module M = 
-    type Lib with
-      interface IM 
-          with member x.M i = i
-    
- 
-  module F = exit 0
-
-
-

tests/fsharpqa/Source/Conformance/ObjectOrientedTypeDefinitions/TypeExtensions/optional/E_TypeExtensionWithInterface01.fs

-// #Conformance #ObjectOrientedTypes #TypeExtensions #Regression
-// Regression for 909525, previously there was no error here
-// <Expects status="error" id="FS0909" span="(5,15-5,33)">All implemented interfaces should be declared on the initial declaration of the type</Expects>
-type System.Random with
-    interface System.IComparable 
-    static member Factory() = 1
-
-exit 1

tests/fsharpqa/Source/Conformance/ObjectOrientedTypeDefinitions/TypeExtensions/optional/env.lst

@@ -3,7 +3,6 @@
 	SOURCE="lib003.fs" SCFLAGS="-a"						# lib003.fs
 	SOURCE="lib004.fs" SCFLAGS="-a"						# lib004.fs
 	SOURCE="lib005.fs" SCFLAGS="-a"						# lib005.fs
-	SOURCE="lib006.fs" SCFLAGS="-a"						# lib006.fs
 	SOURCE="E_NotInModule.fs" SCFLAGS="-r:lib000.dll --test:ErrorRanges"	# E_NotInModule.fs
 	SOURCE="ShortNamesAllowed.fs" SCFLAGS="-r:lib000.dll"			# ShortNamesAllowed.fs
 	SOURCE="E_ModuleNotOpen.fs" SCFLAGS="-r:lib000.dll --test:ErrorRanges"	# E_ModuleNotOpen.fs
@@ -13,8 +12,6 @@
 	SOURCE="typeext_opt004.fs" SCFLAGS="-r:lib004.dll" 			# typeext_opt004.fs
 	SOURCE="typeext_opt005.fs" SCFLAGS="-r:lib005.dll" 				# typeext_opt005.fs
 	SOURCE="E_typeext_opt005.fs" SCFLAGS="-r:lib005.dll --test:ErrorRanges" 	# E_typeext_opt005.fs
-	SOURCE="typeext_opt006.fs" SCFLAGS="-r:lib006.dll --test:ErrorRanges"	# typeext_opt006.fs
 	SOURCE="typeext_opt007.fs" SCFLAGS="-r:lib001.dll"			# typeext_opt007.fs
 	SOURCE="typeext_opt008.fs" SCFLAGS="-r:lib001.dll --test:ErrorRanges"	# typeext_opt008.fs
-	SOURCE=E_TypeExtensionWithInterface01.fs  SCFLAGS="--test:ErrorRanges"	# E_TypeExtensionWithInterface01.fs
 	SOURCE=E_CrossModule01.fs   SCFLAGS="--test:ErrorRanges"			# E_CrossModule01.fs

tests/fsharpqa/Source/Conformance/ObjectOrientedTypeDefinitions/TypeExtensions/optional/lib006.fs

-// #Conformance #ObjectOrientedTypes #TypeExtensions  
-#light
-namespace NS
-    type IM = 
-      interface
-        abstract M : int -> int
-      end
-      
-    type Lib() =
-      class
-          member x.Prop = 1
-     end
- 

tests/fsharpqa/Source/Conformance/ObjectOrientedTypeDefinitions/TypeExtensions/optional/typeext_opt006.fs

-// #Regression #Conformance #ObjectOrientedTypes #TypeExtensions  
-//<Expects id="FS0909" span="(7,17-7,19)" status="error">All implemented interfaces should be declared on the initial declaration of the type</Expects>
-
-namespace NS
-  module M = 
-    type Lib with
-      interface IM 
-          with member x.M i = i
-  
-  module F = exit 0
-
-
-

tests/fsharpqa/Source/Diagnostics/General/W_InterfaceImplementationInAugmentation01a.fs

-// #Regression #Diagnostics 
-// Regression test for FSHARP1.0:1273
-// Give warning on use of interface and/or override implementations in augmentations
-//
-//<Expects id="FS0069" span="(18,23-18,24)" status="warning"></Expects>
-
-
-
-type I = interface
-           abstract M : int
-         end
-
-type T2b2 = class
-            interface I
-           end
-           
-type T2b2 with
-            interface I with 
-               member a.M = 3
-            end
-         end
-         

tests/fsharpqa/Source/Diagnostics/General/W_InterfaceImplementationInAugmentation01b.fs

-// #Regression #Diagnostics 
-// Regression test for FSHARP1.0:1273
-// Give warning on use of interface and/or override implementations in augmentations
-//<Expects id="FS0069" span="(26,23-26,25)" status="warning">Interface implementations in augmentations are now deprecated\. Interface implementations should be given on the initial declaration of a type\.$</Expects>
-
-type I = interface
-           abstract M : int
-         end
-         
-type I2 = interface
-           inherit I
-          end
-
-type I3 = interface
-           inherit I2
-         end
-type I4 = interface
-           inherit I3
-         end
-
-type T2b2 = class
-            interface I4
-           end
-           
-type T2b2 with
-            interface I4 with 
-               member a.M = 3
-            end
-         end
-
-

tests/fsharpqa/Source/Diagnostics/General/W_InterfaceImplementationInAugmentation02a.fs

-// #Regression #Diagnostics 
-// Regression test for FSHARP1.0:1273
-// Give warning on use of interface and/or override implementations in augmentations
-//<Expects id="FS0069" span="(27,23-27,25)" status="warning">Interface implementations in augmentations are now deprecated\. Interface implementations should be given on the initial declaration of a type\.$</Expects>
-
-type I = interface
-         end
-         
-type I2 = interface
-           inherit I
-          end
-
-type I3 = interface
-           inherit I2
-          end
-          
-type I4 = interface
-           inherit I3
-           abstract M : int
-          end
-
-type T2b2 = class
-             interface I4
-            end
-           
-type T2b2 with
-            interface I4 with 
-               member a.M = 3
-            end
-          end

tests/fsharpqa/Source/Diagnostics/General/W_OverrideImplementationInAugmentation01b.fs

-// #Regression #Diagnostics 
-// Regression test for FSHARP1.0:1273
-// Give warning on use of interface and/or override implementations in augmentations
-//
-//<Expects id="FS0060" span="(13,21-13,24)" status="warning"></Expects>
-module M
-
-type T2b = class
-            abstract M : int
-            //default a.M = 3
-           end
-type T2b with
-            default x.M = 0    // warning FS0060: Override implementations should be given as part of the initial declaration of a type. While the current language specification allows overrides implementations in augmentations, this is likely to be deprecated in a future revision of the language
-        end

tests/fsharpqa/Source/Diagnostics/General/W_OverrideImplementationInAugmentation02a.fs

-// #Regression #Diagnostics 
-// Regression test for FSHARP1.0:1273
-// Give warning on use of interface and/or override implementations in augmentations
-//
-//<Expects id="FS0060" span="(13,22-13,25)" status="warning"></Expects>
-//<Expects id="FS0001" span="(13,28-13,31)" status="error"></Expects>
-
-type T2 = class
-            abstract M : int
-            //default a.M = 3
-           end
-type T2 with
-            override x.M = 0.0       // warning + error    
-        end

tests/fsharpqa/Source/Diagnostics/General/env.lst

@@ -93,12 +93,7 @@ NoMT	SOURCE=E_MissingSourceFile04.fs SCFLAGS="--exec doesnotexist.fs" FSIMODE=PI
 	SOURCE=E_StructMustHaveAtLeastOneField.fs SCFLAGS="--test:ErrorRanges"	# E_StructMustHaveAtLeastOneField.fs
 	SOURCE=E_UnexpectedSymbol01.fs            SCFLAGS="--test:ErrorRanges"	# E_UnexpectedSymbol01.fs
 
-	SOURCE=W_InterfaceImplementationInAugmentation01a.fs SCFLAGS="--test:ErrorRanges"	# W_InterfaceImplementationInAugmentation01a.fs
-	SOURCE=W_InterfaceImplementationInAugmentation01b.fs SCFLAGS="--test:ErrorRanges"	# W_InterfaceImplementationInAugmentation01b.fs
-	SOURCE=W_InterfaceImplementationInAugmentation02a.fs SCFLAGS="--test:ErrorRanges"	# W_InterfaceImplementationInAugmentation02a.fs
 	SOURCE=W_OverrideImplementationInAugmentation01a.fs  SCFLAGS="--test:ErrorRanges -a"	# W_OverrideImplementationInAugmentation01a.fs
-	SOURCE=W_OverrideImplementationInAugmentation01b.fs  SCFLAGS="--test:ErrorRanges -a"	# W_OverrideImplementationInAugmentation01b.fs
-	SOURCE=W_OverrideImplementationInAugmentation02a.fs  SCFLAGS="--test:ErrorRanges"	# W_OverrideImplementationInAugmentation02a.fs
 	SOURCE=W_OverrideImplementationInAugmentation02b.fs  SCFLAGS="--test:ErrorRanges"	# W_OverrideImplementationInAugmentation02b.fs
 	SOURCE=W_OverrideImplementationInAugmentation03a.fs  SCFLAGS="--test:ErrorRanges -a"	# W_OverrideImplementationInAugmentation03a.fs
 	SOURCE=W_OverrideImplementationInAugmentation03b.fs  SCFLAGS="--test:ErrorRanges -a"	# W_OverrideImplementationInAugmentation03b.fs