[RFC FS-1060] Nullness checking

.fantomasignore

@@ -88,6 +88,23 @@ src/FSharp.Core/Query.fs
 src/FSharp.Core/seqcore.fs
 
 
+# fsharp  (to investigate)
+
+**/TypeProviders.fsi
+**/tainted.fsi
+
+# uses nullness features
+
+**/DependencyProvider.fsi
+src/FSharp.Core/array.fs
+src/FSharp.Core/option.fsi
+src/FSharp.Core/option.fs
+src/fsi/console.fs
+src/FSharp.Build/FSharpCommandLineBuilder.fs
+src/Compiler/Utilities/sformat.fs
+src/Compiler/Utilities/illib.fsi
+src/Compiler/Utilities/illib.fs
+
 # Fantomas limitations on implementation files  (to investigate)
 
 src/Compiler/AbstractIL/ilwrite.fs

.gitignore

@@ -127,3 +127,6 @@ nCrunchTemp_*
 tests/FSharp.Compiler.Service.Tests/FSharp.CompilerService.SurfaceArea.netstandard.actual
 *.vsp
 /tests/AheadOfTime/Trimming/output.txt
+*.svclog
+micro.exe
+positive.exe

FSharp.Benchmarks.sln

@@ -1,5 +1,4 @@
-
-Microsoft Visual Studio Solution File, Format Version 12.00
+Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.1.32113.165
 MinimumVisualStudioVersion = 10.0.40219.1

FSharp.Profiles.props

@@ -1,6 +1,36 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information. -->
 <Project>
+  <PropertyGroup>
+    <!-- This turns on/off the use of the feature within the codebase -->
+    <!-- The default is off - it is selectively enabled -->
+    <CheckNulls Condition="'$(CheckNulls)' == ''">false</CheckNulls>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(FSHARPCORE_USE_PACKAGE)' == 'true'">
+    <!-- nullness checking isn't possible when using shipped FSharp.Core package until it's updated -->
+    <CheckNulls>false</CheckNulls>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)' == 'Proto'">
+    <CheckNulls>false</CheckNulls>
+    <DefineConstants>NO_CHECKNULLS;BUILDING_WITH_LKG;NO_NULLCHECKING_LIB_SUPPORT;$(DefineConstants)</DefineConstants>
+    <NullCheckingSupportInLibrary>false</NullCheckingSupportInLibrary>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Configuration)' != 'Proto' and '$(BUILDING_USING_DOTNET)' != 'true'"> 
+    <OtherFlags>$(OtherFlags) /langversion:preview</OtherFlags>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(CheckNulls)' == 'true'">
+    <OtherFlags>$(OtherFlags) /checknulls</OtherFlags>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(CheckNulls)' == 'false'">
+    <!-- 3271: warning nullness annotations being ignored -->
+    <NoWarn>$(NoWarn);3271</NoWarn>
+    <DefineConstants>NO_CHECKNULLS;$(DefineConstants)</DefineConstants>
+  </PropertyGroup>
 
   <Choose>
     <When Condition=" '$(TargetFrameworkIdentifier)' == '.NETFramework' ">

docs/release-notes/.FSharp.Compiler.Service/9.0.100.md

@@ -1,9 +1,13 @@
 ### Fixed
+
 * Compiler hangs when compiling inline recursive invocation ([Issue #17376](https://github.com/dotnet/fsharp/issues/17376), [PR #17394](https://github.com/dotnet/fsharp/pull/17394))
 
 ### Added
 
+* Support for nullable reference types ([PR #15181](https://github.com/dotnet/fsharp/pull/15181))
+
 ### Changed
+
 * Change compiler default setting realsig+ when building assemblies ([Issue #17384](https://github.com/dotnet/fsharp/issues/17384), [PR #17378](https://github.com/dotnet/fsharp/pull/17385))
 * Change compiler default setting for compressedMetadata ([Issue #17379](https://github.com/dotnet/fsharp/issues/17379), [PR #17383](https://github.com/dotnet/fsharp/pull/17383))
 

docs/release-notes/.Language/preview.md

@@ -2,6 +2,7 @@
 
 * Speed up `for x in xs -> …` in list & array comprehensions in certain scenarios. ([PR #16948](https://github.com/dotnet/fsharp/pull/16948))
 * Lower integral ranges to fast loops in more cases and optimize list and array construction from ranges. ([PR #16650](https://github.com/dotnet/fsharp/pull/16650), [PR #16832](https://github.com/dotnet/fsharp/pull/16832))
+* Support for nullable reference types ([PR #15181](https://github.com/dotnet/fsharp/pull/15181))
 * Better generic unmanaged structs handling. ([Language suggestion #692](https://github.com/fsharp/fslang-suggestions/issues/692), [PR #12154](https://github.com/dotnet/fsharp/pull/12154))
 * Bidirectional F#/C# interop for 'unmanaged' constraint. ([PR #12154](https://github.com/dotnet/fsharp/pull/12154))
 * Make `.Is*` discriminated union properties visible. ([Language suggestion #222](https://github.com/fsharp/fslang-suggestions/issues/222), [PR #16341](https://github.com/dotnet/fsharp/pull/16341))

src/Compiler/AbstractIL/il.fs

@@ -2629,6 +2629,7 @@ type ILTypeDef
         attributes: TypeAttributes,
         layout: ILTypeDefLayout,
         implements: ILTypes,
+        implementsCustomAttrs: (ILAttributesStored * int) list option,
         genericParams: ILGenericParameterDefs,
         extends: ILType option,
         methods: ILMethodDefs,
@@ -2651,6 +2652,7 @@ type ILTypeDef
         attributes,
         layout,
         implements,
+        implementsCustomAttrs,
         genericParams,
         extends,
         methods,
@@ -2667,6 +2669,7 @@ type ILTypeDef
             attributes,
             layout,
             implements,
+            implementsCustomAttrs,
             genericParams,
             extends,
             methods,
@@ -2677,7 +2680,7 @@ type ILTypeDef
             properties,
             additionalFlags,
             storeILSecurityDecls securityDecls,
-            customAttrs,
+            storeILCustomAttrs customAttrs,
             NoMetadataIdx
         )
 
@@ -2693,6 +2696,8 @@ type ILTypeDef
 
     member _.Implements = implements
 
+    member _.ImplementsCustomAttrs = implementsCustomAttrs
+
     member _.Extends = extends
 
     member _.Methods = methods
@@ -2732,7 +2737,8 @@ type ILTypeDef
             ?properties,
             ?newAdditionalFlags,
             ?customAttrs,
-            ?securityDecls
+            ?securityDecls,
+            ?implementsCustomAttrs
         ) =
         ILTypeDef(
             name = defaultArg name x.Name,
@@ -2741,6 +2747,7 @@ type ILTypeDef
             genericParams = defaultArg genericParams x.GenericParams,
             nestedTypes = defaultArg nestedTypes x.NestedTypes,
             implements = defaultArg implements x.Implements,
+            implementsCustomAttrs = defaultArg implementsCustomAttrs x.ImplementsCustomAttrs,
             extends = defaultArg extends x.Extends,
             methods = defaultArg methods x.Methods,
             securityDecls = defaultArg securityDecls x.SecurityDecls,
@@ -2749,7 +2756,7 @@ type ILTypeDef
             events = defaultArg events x.Events,
             properties = defaultArg properties x.Properties,
             additionalFlags = defaultArg newAdditionalFlags additionalFlags,
-            customAttrs = defaultArg customAttrs (storeILCustomAttrs x.CustomAttrs)
+            customAttrs = defaultArg customAttrs (x.CustomAttrs)
         )
 
     member x.CustomAttrs: ILAttributes =
@@ -3439,6 +3446,11 @@ type ILGlobals(primaryScopeRef: ILScopeRef, equivPrimaryAssemblyRefs: ILAssembly
 
     let mkSysILTypeRef nm = mkILTyRef (primaryScopeRef, nm)
 
+    let byteIlType = ILType.Value(mkILNonGenericTySpec (mkSysILTypeRef tname_Byte))
+
+    let stringIlType =
+        mkILBoxedType (mkILNonGenericTySpec (mkSysILTypeRef tname_String))
+
     member _.primaryAssemblyScopeRef = primaryScopeRef
 
     member x.primaryAssemblyRef =
@@ -3456,7 +3468,7 @@ type ILGlobals(primaryScopeRef: ILScopeRef, equivPrimaryAssemblyRefs: ILAssembly
 
     member val typ_Object = mkILBoxedType (mkILNonGenericTySpec (mkSysILTypeRef tname_Object))
 
-    member val typ_String = mkILBoxedType (mkILNonGenericTySpec (mkSysILTypeRef tname_String))
+    member val typ_String = stringIlType
 
     member val typ_Array = mkILBoxedType (mkILNonGenericTySpec (mkSysILTypeRef tname_Array))
 
@@ -3470,7 +3482,11 @@ type ILGlobals(primaryScopeRef: ILScopeRef, equivPrimaryAssemblyRefs: ILAssembly
 
     member val typ_Int64 = ILType.Value(mkILNonGenericTySpec (mkSysILTypeRef tname_Int64))
 
-    member val typ_Byte = ILType.Value(mkILNonGenericTySpec (mkSysILTypeRef tname_Byte))
+    member val typ_Byte = byteIlType
+
+    member val typ_ByteArray = ILType.Array(ILArrayShape.SingleDimensional, byteIlType)
+
+    member val typ_StringArray = ILType.Array(ILArrayShape.SingleDimensional, stringIlType)
 
     member val typ_UInt16 = ILType.Value(mkILNonGenericTySpec (mkSysILTypeRef tname_UInt16))
 
@@ -4231,12 +4247,13 @@ let mkILGenericClass (nm, access, genparams, extends, impl, methods, fields, nes
         attributes = attributes,
         genericParams = genparams,
         implements = impl,
+        implementsCustomAttrs = None,
         layout = ILTypeDefLayout.Auto,
         extends = Some extends,
         methods = methods,
         fields = fields,
         nestedTypes = nestedTypes,
-        customAttrs = storeILCustomAttrs attrs,
+        customAttrs = attrs,
         methodImpls = emptyILMethodImpls,
         properties = props,
         events = events,
@@ -4255,12 +4272,13 @@ let mkRawDataValueTypeDef (iltyp_ValueType: ILType) (nm, size, pack) =
              ||| TypeAttributes.BeforeFieldInit
              ||| TypeAttributes.AnsiClass),
         implements = [],
+        implementsCustomAttrs = None,
         extends = Some iltyp_ValueType,
         layout = ILTypeDefLayout.Explicit { Size = Some size; Pack = Some pack },
         methods = emptyILMethods,
         fields = emptyILFields,
         nestedTypes = emptyILTypeDefs,
-        customAttrs = emptyILCustomAttrsStored,
+        customAttrs = emptyILCustomAttrs,
         methodImpls = emptyILMethodImpls,
         properties = emptyILProperties,
         events = emptyILEvents,

src/Compiler/AbstractIL/il.fsi

@@ -869,7 +869,13 @@ type ILAttributes =
 
 /// Represents the efficiency-oriented storage of ILAttributes in another item.
 [<NoEquality; NoComparison>]
-type ILAttributesStored
+type ILAttributesStored =
+    /// Computed by ilread.fs based on metadata index
+    | Reader of (int32 -> ILAttribute[])
+    /// Already computed
+    | Given of ILAttributes
+
+    member GetCustomAttrs: int32 -> ILAttributes
 
 /// Method parameters and return values.
 [<RequireQualifiedAccess; NoEquality; NoComparison>]
@@ -1070,6 +1076,8 @@ type ILMethodDef =
     member IsEntryPoint: bool
     member GenericParams: ILGenericParameterDefs
     member CustomAttrs: ILAttributes
+    member MetadataIndex: int32
+    member CustomAttrsStored: ILAttributesStored
     member ParameterTypes: ILTypes
     member IsIL: bool
     member Code: ILCode option
@@ -1243,6 +1251,10 @@ type ILFieldDef =
 
     member CustomAttrs: ILAttributes
 
+    member MetadataIndex: int32
+
+    member CustomAttrsStored: ILAttributesStored
+
     member IsStatic: bool
 
     member IsSpecialName: bool
@@ -1326,6 +1338,8 @@ type ILEventDef =
     member FireMethod: ILMethodRef option
     member OtherMethods: ILMethodRef list
     member CustomAttrs: ILAttributes
+    member MetadataIndex: int32
+    member CustomAttrsStored: ILAttributesStored
     member IsSpecialName: bool
     member IsRTSpecialName: bool
 
@@ -1388,6 +1402,8 @@ type ILPropertyDef =
     member Init: ILFieldInit option
     member Args: ILTypes
     member CustomAttrs: ILAttributes
+    member MetadataIndex: int32
+    member CustomAttrsStored: ILAttributesStored
     member IsSpecialName: bool
     member IsRTSpecialName: bool
 
@@ -1498,6 +1514,7 @@ type ILTypeDef =
         attributes: TypeAttributes *
         layout: ILTypeDefLayout *
         implements: ILTypes *
+        implementsCustomAttrs: (ILAttributesStored * int) list option *
         genericParams: ILGenericParameterDefs *
         extends: ILType option *
         methods: ILMethodDefs *
@@ -1518,6 +1535,7 @@ type ILTypeDef =
         attributes: TypeAttributes *
         layout: ILTypeDefLayout *
         implements: ILTypes *
+        implementsCustomAttrs: (ILAttributesStored * int) list option *
         genericParams: ILGenericParameterDefs *
         extends: ILType option *
         methods: ILMethodDefs *
@@ -1528,7 +1546,7 @@ type ILTypeDef =
         properties: ILPropertyDefs *
         additionalFlags: ILTypeDefAdditionalFlags *
         securityDecls: ILSecurityDecls *
-        customAttrs: ILAttributesStored ->
+        customAttrs: ILAttributes ->
             ILTypeDef
 
     member Name: string
@@ -1537,6 +1555,7 @@ type ILTypeDef =
     member Layout: ILTypeDefLayout
     member NestedTypes: ILTypeDefs
     member Implements: ILTypes
+    member ImplementsCustomAttrs: (ILAttributesStored * int) list option
     member Extends: ILType option
     member Methods: ILMethodDefs
     member SecurityDecls: ILSecurityDecls
@@ -1545,6 +1564,8 @@ type ILTypeDef =
     member Events: ILEventDefs
     member Properties: ILPropertyDefs
     member CustomAttrs: ILAttributes
+    member MetadataIndex: int32
+    member CustomAttrsStored: ILAttributesStored
     member IsClass: bool
     member IsStruct: bool
     member IsInterface: bool
@@ -1593,8 +1614,9 @@ type ILTypeDef =
         ?events: ILEventDefs *
         ?properties: ILPropertyDefs *
         ?newAdditionalFlags: ILTypeDefAdditionalFlags *
-        ?customAttrs: ILAttributesStored *
-        ?securityDecls: ILSecurityDecls ->
+        ?customAttrs: ILAttributes *
+        ?securityDecls: ILSecurityDecls *
+        ?implementsCustomAttrs: (ILAttributesStored * int) list option ->
             ILTypeDef
 
 /// Represents a prefix of information for ILTypeDef.
@@ -1890,11 +1912,13 @@ type internal ILGlobals =
     member typ_Enum: ILType
     member typ_Object: ILType
     member typ_String: ILType
+    member typ_StringArray: ILType
     member typ_Type: ILType
     member typ_Array: ILType
     member typ_IntPtr: ILType
     member typ_UIntPtr: ILType
     member typ_Byte: ILType
+    member typ_ByteArray: ILType
     member typ_Int16: ILType
     member typ_Int32: ILType
     member typ_Int64: ILType

src/Compiler/AbstractIL/ilmorph.fs

@@ -378,7 +378,7 @@ let rec tdef_ty2ty_ilmbody2ilmbody_mdefs2mdefs isInKnownSet enc fs (tdef: ILType
         methodImpls = mimpls_ty2ty fTyInCtxtR tdef.MethodImpls,
         events = edefs_ty2ty fTyInCtxtR tdef.Events,
         properties = pdefs_ty2ty fTyInCtxtR tdef.Properties,
-        customAttrs = storeILCustomAttrs (cattrs_ty2ty fTyInCtxtR tdef.CustomAttrs)
+        customAttrs = cattrs_ty2ty fTyInCtxtR tdef.CustomAttrs
     )
 
 and tdefs_ty2ty_ilmbody2ilmbody_mdefs2mdefs isInKnownSet enc fs tdefs =