Gate exception field serialization behind langversion 11

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -37,7 +37,7 @@
 * Fix signature generation: backtick escaping for identifiers containing backticks. ([Issue #15389](https://github.com/dotnet/fsharp/issues/15389), [PR #19586](https://github.com/dotnet/fsharp/pull/19586))
 * Fix signature generation: `private` keyword placement for prefix-style type abbreviations. ([Issue #15560](https://github.com/dotnet/fsharp/issues/15560), [PR #19586](https://github.com/dotnet/fsharp/pull/19586))
 * Fix signature generation: missing `[<Class>]` attribute for types without visible constructors. ([Issue #16531](https://github.com/dotnet/fsharp/issues/16531), [PR #19586](https://github.com/dotnet/fsharp/pull/19586))
-* Fix F# exception serialization now preserves fields. (Issue [#878](https://github.com/dotnet/fsharp/issues/878), [PR #19342](https://github.com/dotnet/fsharp/pull/19342))
+* Fix F# exception serialization now preserves fields (gated behind `--langversion:11`). (Issue [#878](https://github.com/dotnet/fsharp/issues/878), [PR #19342](https://github.com/dotnet/fsharp/pull/19342), [PR #19746](https://github.com/dotnet/fsharp/pull/19746))
 * Fix methods being tagged as `Member` instead of `Method` in tooltips. ([Issue #10540](https://github.com/dotnet/fsharp/issues/10540), [PR #19507](https://github.com/dotnet/fsharp/pull/19507))
 * Fix Debug-mode compilation when mixing resumable and standard computation expressions. ([Issue #19625](https://github.com/dotnet/fsharp/issues/19625), [PR #19630](https://github.com/dotnet/fsharp/pull/19630))
 * IlxGen: fix missing CompilationMapping attribute for generic values ([PR #19643](https://github.com/dotnet/fsharp/pull/19643))
@@ -60,5 +60,6 @@
 ### Changed
 
 * Improvements in error and warning messages: new error FS3885 when `let!`/`use!` is the final expression in a computation expression; new warning FS3886 when a list literal contains a single tuple element (likely missing `;` separator); improved wording for FS0003, FS0025, FS0039, FS0072, FS0247, FS0597, FS0670, FS3082, and SRTP operator-not-in-scope hints. ([PR #19398](https://github.com/dotnet/fsharp/pull/19398))
+* Exception field serialization (`GetObjectData` and field-restoring constructor) is now gated behind `langversion:11` (`LanguageFeature.ExceptionFieldSerializationSupport`). With langversion ≤10, exception codegen is unchanged from pre-#19342 behavior. ([PR #19746](https://github.com/dotnet/fsharp/pull/19746))
 
 ### Breaking Changes

src/Compiler/CodeGen/IlxGen.fs

@@ -12271,11 +12271,10 @@ and GenExnDef cenv mgbuf eenv m (exnc: Tycon) : ILTypeRef option =
                 []
 
         let serializationRelatedMembers =
-            // do not emit serialization related members if target framework lacks SerializationInfo or StreamingContext
             match g.iltyp_SerializationInfo, g.iltyp_StreamingContext with
             | Some serializationInfoType, Some streamingContextType ->
 
-                let emitSerializationFieldIL emitPerField =
+                let emitFieldSerializationIL emitPerField =
                     [
                         for (_, ilFieldName, ilPropType, _) in fieldNamesAndTypes do
                             yield! emitPerField ilFieldName ilPropType
@@ -12285,7 +12284,7 @@ and GenExnDef cenv mgbuf eenv m (exnc: Tycon) : ILTypeRef option =
                     ty.IsNominal && ty.Boxity = ILBoxity.AsValue
 
                 let ilInstrsToRestoreFields =
-                    emitSerializationFieldIL (fun ilFieldName ilPropType ->
+                    emitFieldSerializationIL (fun ilFieldName ilPropType ->
                         [
                             mkLdarg0
                             mkLdarg 1us
@@ -12318,10 +12317,10 @@ and GenExnDef cenv mgbuf eenv m (exnc: Tycon) : ILTypeRef option =
                             mkNormalStfld (mkILFieldSpecInTy (ilThisTy, ilFieldName, ilPropType))
                         ])
 
-                // FSharp.Core is SecurityTransparent and cannot override SecurityCritical
-                // Exception.GetObjectData, so field restoration would be unbalanced — skip it.
-                let shouldRestoreFields =
-                    not g.compilingFSharpCore && not fieldNamesAndTypes.IsEmpty
+                let emitFieldSerialization =
+                    cenv.g.langVersion.SupportsFeature(LanguageFeature.ExceptionFieldSerializationSupport)
+                    && not g.compilingFSharpCore
+                    && not fieldNamesAndTypes.IsEmpty
 
                 let ilInstrsForSerialization =
                     [
@@ -12330,7 +12329,10 @@ and GenExnDef cenv mgbuf eenv m (exnc: Tycon) : ILTypeRef option =
                         mkLdarg 2us
                         mkNormalCall (mkILCtorMethSpecForTy (g.iltyp_Exception, [ serializationInfoType; streamingContextType ]))
                     ]
-                    @ (if shouldRestoreFields then ilInstrsToRestoreFields else [])
+                    @ (if emitFieldSerialization then
+                           ilInstrsToRestoreFields
+                       else
+                           [])
                     |> nonBranchingInstrsToCode
 
                 let ilCtorDefForSerialization =
@@ -12344,73 +12346,66 @@ and GenExnDef cenv mgbuf eenv m (exnc: Tycon) : ILTypeRef option =
                     )
                     |> AddNonUserCompilerGeneratedAttribs g
 
-                let ilInstrsToSaveFields =
-                    emitSerializationFieldIL (fun ilFieldName ilPropType ->
+                if not emitFieldSerialization then
+                    [ ilCtorDefForSerialization ]
+                else
+                    let ilInstrsToSaveFields =
+                        emitFieldSerializationIL (fun ilFieldName ilPropType ->
+                            [
+                                mkLdarg 1us
+                                I_ldstr ilFieldName
+                                mkLdarg0
+                                mkNormalLdfld (mkILFieldSpecInTy (ilThisTy, ilFieldName, ilPropType))
+
+                                if isILValueType ilPropType then
+                                    I_box ilPropType
+
+                                mkNormalCallvirt (
+                                    mkILNonGenericInstanceMethSpecInTy (
+                                        serializationInfoType,
+                                        "AddValue",
+                                        [ g.ilg.typ_String; g.ilg.typ_Object ],
+                                        ILType.Void
+                                    )
+                                )
+                            ])
+
+                    let ilInstrsForGetObjectData =
                         [
-                            mkLdarg 1us
-                            I_ldstr ilFieldName
                             mkLdarg0
-                            mkNormalLdfld (mkILFieldSpecInTy (ilThisTy, ilFieldName, ilPropType))
-
-                            if isILValueType ilPropType then
-                                I_box ilPropType
-
-                            mkNormalCallvirt (
+                            mkLdarg 1us
+                            mkLdarg 2us
+                            mkNormalCall (
                                 mkILNonGenericInstanceMethSpecInTy (
-                                    serializationInfoType,
-                                    "AddValue",
-                                    [ g.ilg.typ_String; g.ilg.typ_Object ],
+                                    g.iltyp_Exception,
+                                    "GetObjectData",
+                                    [ serializationInfoType; streamingContextType ],
                                     ILType.Void
                                 )
                             )
-                        ])
+                        ]
+                        @ ilInstrsToSaveFields
+                        |> nonBranchingInstrsToCode
 
-                let ilInstrsForGetObjectData =
-                    [
-                        mkLdarg0
-                        mkLdarg 1us
-                        mkLdarg 2us
-                        mkNormalCall (
-                            mkILNonGenericInstanceMethSpecInTy (
-                                g.iltyp_Exception,
+                    let ilGetObjectDataDef =
+                        let securityCriticalAttr =
+                            mkILCustomAttribute (g.attrib_SecurityCriticalAttribute.TypeRef, [], [], [])
+
+                        let mdef =
+                            mkILNonGenericVirtualInstanceMethod (
                                 "GetObjectData",
-                                [ serializationInfoType; streamingContextType ],
-                                ILType.Void
+                                ILMemberAccess.Public,
+                                [
+                                    mkILParamNamed ("info", serializationInfoType)
+                                    mkILParamNamed ("context", streamingContextType)
+                                ],
+                                mkILReturn ILType.Void,
+                                mkMethodBody (false, [], 8, ilInstrsForGetObjectData, None, eenv.imports)
                             )
-                        )
-                    ]
-                    @ ilInstrsToSaveFields
-                    |> nonBranchingInstrsToCode
 
-                let ilGetObjectDataDef =
-                    let mdef =
-                        mkILNonGenericVirtualInstanceMethod (
-                            "GetObjectData",
-                            ILMemberAccess.Public,
-                            [
-                                mkILParamNamed ("info", serializationInfoType)
-                                mkILParamNamed ("context", streamingContextType)
-                            ],
-                            mkILReturn ILType.Void,
-                            mkMethodBody (false, [], 8, ilInstrsForGetObjectData, None, eenv.imports)
-                        )
-
-                    // SecurityCritical is required for .NET Framework where Exception.GetObjectData is security-critical
-                    let securityCriticalAttr =
-                        mkILCustomAttribute (g.attrib_SecurityCriticalAttribute.TypeRef, [], [], [])
+                        mdef.With(customAttrs = mkILCustomAttrs [ securityCriticalAttr ])
+                        |> AddNonUserCompilerGeneratedAttribs g
 
-                    mdef.With(customAttrs = mkILCustomAttrs [ securityCriticalAttr ])
-                    |> AddNonUserCompilerGeneratedAttribs g
-
-                // FSharp.Core has [assembly: SecurityTransparent], making all code transparent.
-                // On .NET Framework, transparent code cannot override SecurityCritical virtual
-                // methods like Exception.GetObjectData. Without GetObjectData to write the fields,
-                // the field-restoring deserialization constructor would crash (fields not in
-                // SerializationInfo). So for FSharp.Core: emit only the base-call ctor (status quo).
-                // For user exceptions: emit both GetObjectData and the field-restoring ctor.
-                if g.compilingFSharpCore || fieldNamesAndTypes.IsEmpty then
-                    [ ilCtorDefForSerialization ]
-                else
                     [ ilCtorDefForSerialization; ilGetObjectDataDef ]
             | _ -> []
 

src/Compiler/FSComp.txt

@@ -1818,3 +1818,4 @@ featurePreprocessorElif,"#elif preprocessor directive"
 3885,parsLetBangCannotBeLastInCE,"'%s' cannot be the final expression in a computation expression. Finish with 'return', 'return!', or a simple expression."
 3886,tcListLiteralWithSingleTupleElement,"This list expression contains a single tuple element. Did you mean to use ';' instead of ',' to separate list elements?"
 3887,ilCustomAttrInvalidArrayElemType,"The type '%s' is not a valid custom attribute argument type. Custom attribute arrays must have elements of primitive types, enums, string, System.Type, or System.Object."
+featureExceptionFieldSerializationSupport,"emit GetObjectData and field-restoring deserialization constructor for exception types"

src/Compiler/Facilities/LanguageFeatures.fs

@@ -108,6 +108,7 @@ type LanguageFeature =
     | MethodOverloadsCache
     | ImplicitDIMCoverage
     | PreprocessorElif
+    | ExceptionFieldSerializationSupport
 
 /// LanguageVersion management
 type LanguageVersion(versionText, ?disabledFeaturesArray: LanguageFeature array) =
@@ -251,6 +252,7 @@ type LanguageVersion(versionText, ?disabledFeaturesArray: LanguageFeature array)
                 // Put stabilized features here for F# 11.0 previews via .NET SDK preview channels
                 LanguageFeature.WarnWhenFunctionValueUsedAsInterpolatedStringArg, languageVersion110
                 LanguageFeature.PreprocessorElif, languageVersion110
+                LanguageFeature.ExceptionFieldSerializationSupport, languageVersion110
 
                 // Difference between languageVersion110 and preview - 11.0 gets turned on automatically by picking a preview .NET 11 SDK
                 // previewVersion is only when "preview" is specified explicitly in project files  and users also need a preview SDK
@@ -453,6 +455,7 @@ type LanguageVersion(versionText, ?disabledFeaturesArray: LanguageFeature array)
         | LanguageFeature.MethodOverloadsCache -> FSComp.SR.featureMethodOverloadsCache ()
         | LanguageFeature.ImplicitDIMCoverage -> FSComp.SR.featureImplicitDIMCoverage ()
         | LanguageFeature.PreprocessorElif -> FSComp.SR.featurePreprocessorElif ()
+        | LanguageFeature.ExceptionFieldSerializationSupport -> FSComp.SR.featureExceptionFieldSerializationSupport ()
 
     /// Get a version string associated with the given feature.
     static member GetFeatureVersionString feature =

src/Compiler/Facilities/LanguageFeatures.fsi

@@ -99,6 +99,7 @@ type LanguageFeature =
     | MethodOverloadsCache
     | ImplicitDIMCoverage
     | PreprocessorElif
+    | ExceptionFieldSerializationSupport
 
 /// LanguageVersion management
 type LanguageVersion =