Init-only & required properties support

eng/Versions.props

@@ -113,8 +113,8 @@
     <SystemRuntimeCompilerServicesUnsafeVersion>6.0.0</SystemRuntimeCompilerServicesUnsafeVersion>
     <SystemValueTupleVersion>4.5.0</SystemValueTupleVersion>
     <!-- VisualStudio package versions  -->
-    <VisualStudioImplementationPackagesVersion>17.2.178-preview</VisualStudioImplementationPackagesVersion>
-    <VisualStudioContractPackagesVersion>17.2.0-preview-1-32131-009</VisualStudioContractPackagesVersion>
+    <VisualStudioImplementationPackagesVersion>17.3.133-preview</VisualStudioImplementationPackagesVersion>
+    <VisualStudioContractPackagesVersion>17.3.0-preview-1-32407-044</VisualStudioContractPackagesVersion>
     <VisualStudioProjectSystemPackagesVersion>17.0.77-pre-g62a6cb5699</VisualStudioProjectSystemPackagesVersion>
     <MicrosoftVisualStudioInteropVersion>$(VisualStudioContractPackagesVersion)</MicrosoftVisualStudioInteropVersion>
     <MicrosoftInternalVisualStudioInteropVersion>$(VisualStudioContractPackagesVersion)</MicrosoftInternalVisualStudioInteropVersion>
@@ -135,7 +135,7 @@
     <EnvDTEVersion>$(VisualStudioContractPackagesVersion)</EnvDTEVersion>
     <EnvDTE80Version>$(VisualStudioContractPackagesVersion)</EnvDTE80Version>
     <!-- Roslyn packages -->
-    <RoslynVersion>4.2.0-3.22154.1</RoslynVersion>
+    <RoslynVersion>4.4.0-1.22360.2</RoslynVersion>
     <MicrosoftCodeAnalysisEditorFeaturesVersion>$(RoslynVersion)</MicrosoftCodeAnalysisEditorFeaturesVersion>
     <MicrosoftCodeAnalysisEditorFeaturesTextVersion>$(RoslynVersion)</MicrosoftCodeAnalysisEditorFeaturesTextVersion>
     <MicrosoftCodeAnalysisEditorFeaturesWpfVersion>$(RoslynVersion)</MicrosoftCodeAnalysisEditorFeaturesWpfVersion>
@@ -144,8 +144,9 @@
     <MicrosoftCodeAnalysisCSharpVersion>$(RoslynVersion)</MicrosoftCodeAnalysisCSharpVersion>
     <MicrosoftCodeAnalysisTestResourcesProprietaryVersion>2.0.28</MicrosoftCodeAnalysisTestResourcesProprietaryVersion>
     <MicrosoftVisualStudioLanguageServicesVersion>$(RoslynVersion)</MicrosoftVisualStudioLanguageServicesVersion>
+
     <!-- Microsoft Build packages -->
-    <MicrosoftBuildOverallPackagesVersion>17.0.0</MicrosoftBuildOverallPackagesVersion>
+    <MicrosoftBuildOverallPackagesVersion>17.1.0</MicrosoftBuildOverallPackagesVersion>
     <MicrosoftBuildVersion>$(MicrosoftBuildOverallPackagesVersion)</MicrosoftBuildVersion>
     <MicrosoftBuildFrameworkVersion>$(MicrosoftBuildOverallPackagesVersion)</MicrosoftBuildFrameworkVersion>
     <MicrosoftBuildTasksCoreVersion>$(MicrosoftBuildOverallPackagesVersion)</MicrosoftBuildTasksCoreVersion>
@@ -169,7 +170,7 @@
     <MicrosoftVisualStudioShellFrameworkVersion>$(VisualStudioContractPackagesVersion)</MicrosoftVisualStudioShellFrameworkVersion>
     <MicrosoftVisualStudioPackageLanguageService150Version>$(VisualStudioContractPackagesVersion)</MicrosoftVisualStudioPackageLanguageService150Version>
     <!-- Misc. Visual Studio packages -->
-    <MicrosoftVisualStudioRpcContractsVersion>17.2.22-alpha</MicrosoftVisualStudioRpcContractsVersion>
+    <MicrosoftVisualStudioRpcContractsVersion>17.3.3-alpha</MicrosoftVisualStudioRpcContractsVersion>
     <MicrosoftVisualStudioComponentModelHostVersion>$(VisualStudioImplementationPackagesVersion)</MicrosoftVisualStudioComponentModelHostVersion>
     <MicrosoftVisualFSharpMicrosoftVisualStudioShellUIInternalVersion>17.0.0</MicrosoftVisualFSharpMicrosoftVisualStudioShellUIInternalVersion>
     <MicrosoftVisualStudioDesignerInterfacesVersion>$(VisualStudioContractPackagesVersion)</MicrosoftVisualStudioDesignerInterfacesVersion>
@@ -185,9 +186,9 @@
     <MicrosoftVisualStudioShellImmutable150Version>15.0.25123-Dev15Preview</MicrosoftVisualStudioShellImmutable150Version>
     <MicrosoftVisualStudioShellInterop160DesignTimeVersion>16.0.1</MicrosoftVisualStudioShellInterop160DesignTimeVersion>
     <MicrosoftVisualStudioShellInterop16DesignTimeVersion>16.0.28924.11111</MicrosoftVisualStudioShellInterop16DesignTimeVersion>
-    <MicrosoftVisualStudioThreadingVersion>17.2.10-alpha</MicrosoftVisualStudioThreadingVersion>
+    <MicrosoftVisualStudioThreadingVersion>17.3.1-alpha</MicrosoftVisualStudioThreadingVersion>
     <MicrosoftVisualStudioUtilitiesVersion>$(VisualStudioContractPackagesVersion)</MicrosoftVisualStudioUtilitiesVersion>
-    <MicrosoftVisualStudioValidationVersion>17.0.46</MicrosoftVisualStudioValidationVersion>
+    <MicrosoftVisualStudioValidationVersion>17.0.53</MicrosoftVisualStudioValidationVersion>
     <MicrosoftVisualStudioWCFReferenceInteropVersion>9.0.30729</MicrosoftVisualStudioWCFReferenceInteropVersion>
     <SystemRuntimeCompilerServicesUnsafeVersion>6.0.0</SystemRuntimeCompilerServicesUnsafeVersion>
     <VSSDKDebuggerVisualizersVersion>12.0.4</VSSDKDebuggerVisualizersVersion>
@@ -216,7 +217,7 @@
     <NUnitLiteVersion>3.11.0</NUnitLiteVersion>
     <NunitXmlTestLoggerVersion>2.1.80</NunitXmlTestLoggerVersion>
     <RoslynToolsSignToolVersion>1.0.0-beta2-dev3</RoslynToolsSignToolVersion>
-    <StreamJsonRpcVersion>2.11.34</StreamJsonRpcVersion>
+    <StreamJsonRpcVersion>2.12.7-alpha</StreamJsonRpcVersion>
     <NerdbankStreamsVersion>2.8.57</NerdbankStreamsVersion>
     <XUnitVersion>2.4.1</XUnitVersion>
     <XUnitRunnerVersion>2.4.2</XUnitRunnerVersion>

src/Compiler/Checking/AttributeChecking.fs

@@ -21,6 +21,8 @@ open FSharp.Compiler.TypeHierarchy
 #if !NO_TYPEPROVIDERS
 open FSharp.Compiler.TypeProviders
 open FSharp.Core.CompilerServices
+open Features
+
 #endif
 
 exception ObsoleteWarning of string * range
@@ -236,8 +238,20 @@ let private CheckILAttributes (g: TcGlobals) isByrefLikeTyconRef cattrs m =
     | Some ([ILAttribElem.String (Some msg) ], _) when not isByrefLikeTyconRef -> 
             WarnD(ObsoleteWarning(msg, m))
     | Some ([ILAttribElem.String (Some msg); ILAttribElem.Bool isError ], _) when not isByrefLikeTyconRef -> 
-        if isError then 
-            ErrorD (ObsoleteError(msg, m))
+        if isError then
+            if g.langVersion.SupportsFeature(LanguageFeature.RequiredPropertiesSupport) then
+                // In some cases C# will generate both ObsoleteAttribute and CompilerFeatureRequiredAttribute.
+                // Specifically, when default constructor is generated for class with any reqired members in them.
+                // ObsoleteAttribute should be ignored if CompilerFeatureRequiredAttribute is present, and its name is "RequiredMembers".
+                // REVIEW: Shall feature names be moved to LanguageFeatures (or elsewhere), and be tied to actual features somehow?
+                let (AttribInfo(tref,_)) = g.attrib_CompilerFeatureRequiredAttribute
+                match TryDecodeILAttribute tref cattrs with
+                | Some([ILAttribElem.String (Some featureName) ], _) when featureName = "RequiredMembers" ->
+                    CompleteD
+                | _ ->
+                    ErrorD (ObsoleteError(msg, m))
+            else
+                ErrorD (ObsoleteError(msg, m))
         else 
             WarnD (ObsoleteWarning(msg, m))
     | Some ([ILAttribElem.String None ], _) when not isByrefLikeTyconRef -> 

src/Compiler/Checking/CheckExpressions.fs

@@ -8964,6 +8964,20 @@ and TcLookupThen cenv overallTy env tpenv mObjExpr objExpr objExprTy longId dela
         // To get better warnings we special case some of the few known mutate-a-struct method names
         let mutates = (if methodName = "MoveNext" || methodName = "GetNextArg" then DefinitelyMutates else PossiblyMutates)
 
+        if g.langVersion.SupportsFeature(LanguageFeature.InitPropertiesSupport) then
+            let minfo = List.head minfos
+
+            // Check, wheter this method has `IsExternalInit`, emit an error diagnostic in this case.
+            let hasInitOnlyMod =
+                match minfo with
+                | ILMeth (_, ilMethInfo, _) ->
+                    match ilMethInfo.ILMethodRef.ReturnType with
+                    | ILType.Modified(_, cls, _) -> cls.FullName = "System.Runtime.CompilerServices.IsExternalInit"
+                    | _ -> false
+                | _ -> false
+            if hasInitOnlyMod then
+                errorR (Error (FSComp.SR.tcGetterForInitOnlyPropertyCannotBeCalled1 methodName, mItem))
+
 #if !NO_TYPEPROVIDERS
         match TryTcMethodAppToStaticConstantArgs cenv env tpenv (minfos, tyArgsOpt, mExprAndItem, mItem) with
         | Some minfoAfterStaticArguments ->
@@ -9010,6 +9024,10 @@ and TcLookupThen cenv overallTy env tpenv mObjExpr objExpr objExprTy longId dela
                 if isNil meths then error (Error (FSComp.SR.tcPropertyIsNotReadable nm, mItem))
                 TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt objArgs mExprAndItem mItem nm ad PossiblyMutates true meths afterResolution NormalValUse args atomicFlag delayed
             else
+
+                if g.langVersion.SupportsFeature(LanguageFeature.RequiredPropertiesSupport) && pinfo.IsSetterInitOnly then
+                    errorR (Error (FSComp.SR.tcInitOnlyPropertyCannotBeSet1 nm, mItem))
+
                 let args = if pinfo.IsIndexer then args else []
                 let mut = (if isStructTy g (tyOfExpr g objExpr) then DefinitelyMutates else PossiblyMutates)
                 TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt objArgs mStmt mItem nm ad mut true meths afterResolution NormalValUse (args @ [expr2]) atomicFlag []
@@ -9713,6 +9731,37 @@ and TcMethodApplication
     // Handle post-hoc property assignments
     let setterExprPrebinders, callExpr3 =
         let expr = callExpr2b
+
+        // Make sure, if apparent type has any required properties, they all are in the `finalAssignedItemSetters`.
+        // If if is a constructor, and it is not marked with `SetsRequiredMembersAttributeAttribute`, then:
+        // 1. Get all properties of the type.
+        // 2. Check if any of them has `IsRequired` set.
+        //      2.1. If there are none, proceed as usual
+        //      2.2. If there are any, make sure all of them (or their setters) are in `finalAssignedItemSetters`.
+        // 3. If some are missing, produce a diagnostic which missing ones.
+        if g.langVersion.SupportsFeature(LanguageFeature.RequiredPropertiesSupport) && finalCalledMethInfo.IsConstructor then
+            let requiredProps = 
+                match finalCalledMethInfo with
+                | ILMeth (_, ilmethInfo, _) ->
+                    if TryFindILAttribute g.attrib_SetsRequiredMembersAttribute ilmethInfo.RawMetadata.CustomAttrs then
+                        []
+                    else     
+                        let props = GetImmediateIntrinsicPropInfosOfType (None, AccessibleFromSomeFSharpCode) g cenv.amap range0 ilmethInfo.ApparentEnclosingType
+                        List.filter (fun (p: PropInfo) -> p.IsRequired ) props
+                | _ -> []
+
+            if requiredProps.Length > 0 then
+                let setterPropNames = 
+                    finalAssignedItemSetters
+                    |> List.choose (function | AssignedItemSetter(_, AssignedPropSetter (pinfo, _, _), _) -> Some pinfo.PropertyName  | _ -> None)
+
+                let missingProps =
+                    requiredProps
+                    |> List.filter (fun pinfo -> not (List.contains pinfo.PropertyName setterPropNames))
+                if missingProps.Length > 0 then
+                    let details = NicePrint.multiLineStringOfPropInfos g cenv.amap mMethExpr env.DisplayEnv missingProps
+                    errorR(Error(FSComp.SR.tcMissingRequiredMembers details, mMethExpr))
+
         if isCheckingAttributeCall then
             [], expr
         elif isNil finalAssignedItemSetters then
@@ -9724,7 +9773,7 @@ and TcMethodApplication
             // Build the expression that mutates the properties on the result of the call
             let setterExprPrebinders, propSetExpr =
                 (mkUnit g mMethExpr, finalAssignedItemSetters) ||> List.mapFold (fun acc assignedItemSetter ->
-                        let argExprPrebinder, action, m = TcSetterArgExpr cenv env denv objExpr ad assignedItemSetter
+                        let argExprPrebinder, action, m = TcSetterArgExpr cenv env denv objExpr ad assignedItemSetter finalCalledMethInfo.IsConstructor
                         argExprPrebinder, mkCompGenSequential m acc action)
 
             // now put them together
@@ -9770,7 +9819,7 @@ and TcMethodApplication
     (callExpr6, finalAttributeAssignedNamedItems, delayed), tpenv
 
 /// For Method(X = expr) 'X' can be a property, IL Field or F# record field
-and TcSetterArgExpr cenv env denv objExpr ad (AssignedItemSetter(id, setter, CallerArg(callerArgTy, m, isOptCallerArg, argExpr))) =
+and TcSetterArgExpr cenv env denv objExpr ad (AssignedItemSetter(id, setter, CallerArg(callerArgTy, m, isOptCallerArg, argExpr))) calledFromConstructor =
     let g = cenv.g
 
     if isOptCallerArg then
@@ -9779,6 +9828,10 @@ and TcSetterArgExpr cenv env denv objExpr ad (AssignedItemSetter(id, setter, Cal
     let argExprPrebinder, action, defnItem =
         match setter with
         | AssignedPropSetter (pinfo, pminfo, pminst) ->
+
+            if g.langVersion.SupportsFeature(LanguageFeature.RequiredPropertiesSupport) && pinfo.IsSetterInitOnly && not calledFromConstructor then
+                errorR (Error (FSComp.SR.tcInitOnlyPropertyCannotBeSet1 pinfo.PropertyName, m))
+
             MethInfoChecks g cenv.amap true None [objExpr] ad m pminfo
             let calledArgTy = List.head (List.head (pminfo.GetParamTypes(cenv.amap, m, pminst)))
             let tcVal = LightweightTcValForUsingInBuildMethodCall g

src/Compiler/Checking/NicePrint.fs

@@ -1552,6 +1552,10 @@ module InfoMemberPrinting =
         layoutType denv retTy ^^
         getterSetter
 
+    let formatPropInfoToBufferFreeStyle g amap m denv os (pinfo: PropInfo) = 
+        let resL = prettyLayoutOfPropInfoFreeStyle g amap m denv pinfo 
+        resL |> bufferL os
+
     let formatMethInfoToBufferFreeStyle amap m denv os (minfo: MethInfo) = 
         let _, resL = prettyLayoutOfMethInfoFreeStyle amap m denv emptyTyparInst minfo 
         resL |> bufferL os
@@ -2461,6 +2465,16 @@ let multiLineStringOfMethInfos infoReader m denv minfos =
      |> List.map (sprintf "%s   %s" Environment.NewLine)
      |> String.concat ""
 
+let stringOfPropInfo g amap m denv pinfo =
+         buildString (fun buf -> InfoMemberPrinting.formatPropInfoToBufferFreeStyle g amap m denv buf pinfo)
+
+/// Convert PropInfos to lines separated by newline including a newline as the first character
+let multiLineStringOfPropInfos g amap m denv pinfos =
+     pinfos
+     |> List.map (stringOfPropInfo g amap m denv)
+     |> List.map (sprintf "%s   %s" Environment.NewLine)
+     |> String.concat ""
+
 /// Convert a ParamData to a string
 let stringOfParamData denv paramData = buildString (fun buf -> InfoMemberPrinting.formatParamDataToBuffer denv buf paramData)
 

src/Compiler/Checking/NicePrint.fsi

@@ -82,6 +82,11 @@ val stringOfMethInfo: infoReader: InfoReader -> m: range -> denv: DisplayEnv ->
 val multiLineStringOfMethInfos:
     infoReader: InfoReader -> m: range -> denv: DisplayEnv -> minfos: MethInfo list -> string
 
+val stringOfPropInfo: g: TcGlobals -> amap: ImportMap -> m: range -> denv: DisplayEnv -> pinfo: PropInfo -> string
+
+val multiLineStringOfPropInfos:
+    g: TcGlobals -> amap: ImportMap -> m: range -> denv: DisplayEnv -> pinfos: PropInfo list -> string
+
 val stringOfParamData: denv: DisplayEnv -> paramData: ParamData -> string
 
 val layoutOfParamData: denv: DisplayEnv -> paramData: ParamData -> Layout

src/Compiler/Checking/infos.fs

@@ -1562,6 +1562,12 @@ type ILPropInfo =
     /// Indicates if the IL property has a 'set' method
     member x.HasSetter = Option.isSome x.RawMetadata.SetMethod
 
+    /// Indidcates whether IL property has an init-only setter (i.e. has the `System.Runtime.CompilerServices.IsExternalInit` modifer)
+    member x.IsSetterInitOnly =
+        match x.SetterMethod.ILMethodRef.ReturnType with
+        | ILType.Modified(_, cls, _) -> cls.FullName = "System.Runtime.CompilerServices.IsExternalInit"
+        | _ -> false
+
     /// Indicates if the IL property is static
     member x.IsStatic = (x.RawMetadata.CallingConv = ILThisConvention.Static)
 
@@ -1575,6 +1581,8 @@ type ILPropInfo =
         (x.HasGetter && x.GetterMethod.IsNewSlot) ||
         (x.HasSetter && x.SetterMethod.IsNewSlot)
 
+    member x.IsRequired = TryFindILAttribute x.TcGlobals.attrib_RequiredMemberAttribute x.RawMetadata.CustomAttrs
+
     /// Get the names and types of the indexer arguments associated with the IL property.
     ///
     /// Any type parameters of the enclosing type are instantiated in the type returned.
@@ -1688,6 +1696,22 @@ type PropInfo =
         | ProvidedProp(_, pi, m) -> pi.PUntaint((fun pi -> pi.CanWrite), m)
 #endif
 
+    member x.IsSetterInitOnly =
+        match x with
+        | ILProp ilpinfo -> ilpinfo.IsSetterInitOnly
+        | FSProp _ -> false
+#if !NO_TYPEPROVIDERS
+        | ProvidedProp _ -> false
+#endif
+
+    member x.IsRequired =
+        match x with
+        | ILProp ilpinfo -> ilpinfo.IsRequired
+        | FSProp _ -> false
+#if !NO_TYPEPROVIDERS
+        | ProvidedProp _ -> false
+#endif
+
     /// Indicates if this is an extension member
     member x.IsExtensionMember =
         match x.ArbitraryValRef with

src/Compiler/Checking/infos.fsi

@@ -695,6 +695,9 @@ type ILPropInfo =
     /// Get the declaring IL type of the IL property, including any generic instantiation
     member ILTypeInfo: ILTypeInfo
 
+    /// Is the property requied (has the RequiredMemberAttribute).
+    member IsRequired: bool
+
     /// Indicates if the IL property is logically a 'newslot', i.e. hides any previous slots of the same name.
     member IsNewSlot: bool
 
@@ -787,6 +790,12 @@ type PropInfo =
     /// Indicates if this property has an associated setter method.
     member HasSetter: bool
 
+    /// Indidcates whether IL property has an init-only setter (i.e. has the `System.Runtime.CompilerServices.IsExternalInit` modifer)
+    member IsSetterInitOnly: bool
+
+    /// Is the property requied (has the RequiredMemberAttribute).
+    member IsRequired: bool
+
     member ImplementedSlotSignatures: SlotSig list
 
     /// Indicates if this property is marked 'override' and thus definitely overrides another property.