From 0c84eb00c709a8571c3dbadc105415e5df779773 Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Tue, 6 Feb 2024 11:12:05 +0100
Subject: [PATCH 1/4] Fsharp.Core Unchecked.nonNull

---
 src/FSharp.Core/prim-types.fs  | 21 +++++++++++++++++++++
 src/FSharp.Core/prim-types.fsi | 22 ++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/src/FSharp.Core/prim-types.fs b/src/FSharp.Core/prim-types.fs
index e1f64380f4a..0144d25dae0 100644
--- a/src/FSharp.Core/prim-types.fs
+++ b/src/FSharp.Core/prim-types.fs
@@ -4434,6 +4434,9 @@ namespace Microsoft.FSharp.Core
              when ^T : sbyte       and ^U : sbyte      = (# "conv.i1" (# "add" x y : int32 #) : sbyte #)
              when ^T : byte        and ^U : byte       = (# "conv.u1" (# "add" x y : uint32 #) : byte #)
              when ^T : string      and ^U : string     = (# "" (String.Concat((# "" x : string #),(# "" y : string #))) : ^T #)
+#if !BUILDING_WITH_LKG && !NO_NULLCHECKING_LIB_SUPPORT
+             when ^T : (string|null) and ^U : (string|null) = (# "" (String.Concat((# "" x : string #),(# "" y : string #))) : string #)
+#endif
              when ^T : decimal     and ^U : decimal    = (# "" (Decimal.op_Addition((# "" x : decimal #),(# "" y : decimal #))) : ^V #)
              // According to the somewhat subtle rules of static optimizations,
              // this condition is used whenever ^T is resolved to a nominal type or witnesses are available
@@ -5346,6 +5349,24 @@ namespace Microsoft.FSharp.Core
             [<CompiledName("Hash")>]
             let inline hash x = GenericHash x
 
+            #if !BUILDING_WITH_LKG && !NO_NULLCHECKING_LIB_SUPPORT
+
+            [<CompiledName("NonNull")>]
+            let inline nonNull (x: 'T | null) : 'T = (# "" x : 'T #)
+
+            [<CompiledName("NonNullQuickPattern")>]
+            let inline (|NonNullQuick|) (value : 'T | null when 'T : not null and 'T : not struct) = nonNull value
+
+            #else
+
+            [<CompiledName("NonNull")>]
+            let inline nonNull (x: 'T ) : 'T = x
+
+            [<CompiledName("NonNullQuickPattern")>]
+            let inline (|NonNullQuick|) (value) = nonNull value
+
+            #endif
+
         module Checked = 
         
             let inline (+) (x: ^T) (y: ^U) : ^V = 
diff --git a/src/FSharp.Core/prim-types.fsi b/src/FSharp.Core/prim-types.fsi
index e3c2bb245b6..feb535ba643 100644
--- a/src/FSharp.Core/prim-types.fsi
+++ b/src/FSharp.Core/prim-types.fsi
@@ -5740,6 +5740,28 @@ namespace Microsoft.FSharp.Core
             [<CompiledName("Hash")>]
             val inline hash: 'T -> int
 
+            /// <summary>Unsafely retypes the value from ('T | null) to 'T without doing any null check at runtime. This is an unsafe operation.</summary>
+            /// <param name="value">The possibly nullable value.</param>
+            /// <returns>The same value as in the input.</returns>
+            [<CompiledName("NonNull")>]
+            [<Experimental("Experimental library feature, requires '--langversion:preview'")>]
+            #if !BUILDING_WITH_LKG && !NO_NULLCHECKING_LIB_SUPPORT
+            val inline nonNull : value: 'T | null -> 'T when 'T : not null and 'T : not struct
+            #else
+            val inline nonNull : value: 'T  -> 'T
+            #endif
+
+            /// <summary>When used in a pattern forgets 'nullness' of the value without any runtime check. This is an unsafe operation, as null check is being skipped and null value can be returned.</summary>
+            /// <param name="value">The value to retype from ('T | null) to 'T .</param>
+            /// <returns>The non-null value.</returns>
+            [<CompiledName("NonNullQuickPattern")>]
+            [<Experimental("Experimental library feature, requires '--langversion:preview'")>]
+            #if !BUILDING_WITH_LKG && !NO_NULLCHECKING_LIB_SUPPORT
+            val inline (|NonNullQuick|) : value: 'T | null -> 'T when 'T : not null and 'T : not struct
+            #else
+            val inline (|NonNullQuick|) : value: 'T  -> 'T
+            #endif
+
         /// <summary>A module of comparison and equality operators that are statically resolved, but which are not fully generic and do not make structural comparison. Opening this
         /// module may make code that relies on structural or generic comparison no longer compile.</summary>
         module NonStructuralComparison = 

From d31de714e3391482892792bd1e40669f07130944 Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Tue, 6 Feb 2024 11:24:49 +0100
Subject: [PATCH 2/4] Update src/FSharp.Core/prim-types.fs

---
 src/FSharp.Core/prim-types.fs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/FSharp.Core/prim-types.fs b/src/FSharp.Core/prim-types.fs
index 0144d25dae0..3ec0b8d19d7 100644
--- a/src/FSharp.Core/prim-types.fs
+++ b/src/FSharp.Core/prim-types.fs
@@ -5352,7 +5352,7 @@ namespace Microsoft.FSharp.Core
             #if !BUILDING_WITH_LKG && !NO_NULLCHECKING_LIB_SUPPORT
 
             [<CompiledName("NonNull")>]
-            let inline nonNull (x: 'T | null) : 'T = (# "" x : 'T #)
+            let inline nonNull (x: 'T | null when 'T : not null and 'T : not struct) : 'T = (# "" x : 'T #)
 
             [<CompiledName("NonNullQuickPattern")>]
             let inline (|NonNullQuick|) (value : 'T | null when 'T : not null and 'T : not struct) = nonNull value

From 5ad24c3987da8371b26c97164633b12160fc4d01 Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Tue, 6 Feb 2024 14:03:03 +0100
Subject: [PATCH 3/4] surface area + tests

---
 .../FSharp.Compiler.ComponentTests.fsproj     |  3 +-
 .../NullableLibraryConstructsTests.fs         | 42 +++++++++++++++++++
 ...p.Core.SurfaceArea.netstandard20.debug.bsl | 28 +++++++------
 ...Core.SurfaceArea.netstandard20.release.bsl | 30 ++++++-------
 ...p.Core.SurfaceArea.netstandard21.debug.bsl | 28 +++++++------
 ...Core.SurfaceArea.netstandard21.release.bsl | 28 +++++++------
 6 files changed, 105 insertions(+), 54 deletions(-)
 create mode 100644 tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs

diff --git a/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj b/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj
index 6fe69ad285a..24823485abf 100644
--- a/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj
+++ b/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj
@@ -225,8 +225,9 @@
 	  <Compile Include="Language\CopyAndUpdateTests.fs" />
 	  <Compile Include="Language\ConstraintIntersectionTests.fs" />
     <Compile Include="Language\BooleanReturningAndReturnTypeDirectedPartialActivePatternTests.fs" />
+    <Compile Include="Language\NullableLibraryConstructsTests.fs" />
     <Compile Include="Language\NullableCsharpImportTests.fs" />
-    <Compile Include="ConstraintSolver\PrimitiveConstraints.fs" />
+	  <Compile Include="ConstraintSolver\PrimitiveConstraints.fs" />
     <Compile Include="ConstraintSolver\MemberConstraints.fs" />
     <Compile Include="ConstraintSolver\ObjInference.fs" />
     <Compile Include="Interop\DeeplyNestedCSharpClasses.fs" />
diff --git a/tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs b/tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs
new file mode 100644
index 00000000000..c68412e7859
--- /dev/null
+++ b/tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs
@@ -0,0 +1,42 @@
+module Language.NullableLibraryConstructs
+
+open Xunit
+open FSharp.Test
+open FSharp.Test.Compiler
+
+let typeCheckWithStrictNullness cu =
+    cu
+    |> withLangVersionPreview
+    |> withCheckNulls
+    |> withWarnOn 3261
+    |> withOptions ["--warnaserror+"]
+    |> typecheck
+
+[<FactForNETCOREAPP>]
+let ``Can unsafely forgive null using Unchecked nonNull function`` () = 
+    FSharp """module MyLibrary
+
+let readAllLines (reader:System.IO.StreamReader) : seq<string> =
+    seq {
+        while not reader.EndOfStream do
+            reader.ReadLine() |> Unchecked.nonNull
+    }
+"""
+    |> asLibrary
+    |> typeCheckWithStrictNullness
+    |> shouldSucceed
+
+[<FactForNETCOREAPP>]
+let ``Can unsafely forgive null using Unchecked NonNullQuick active pattern`` () = 
+    FSharp """module MyLibrary
+
+let readAllLines (reader:System.IO.StreamReader) : seq<string> =
+    seq {
+        while not reader.EndOfStream do
+            match reader.ReadLine() with
+            | Unchecked.NonNullQuick line -> yield line
+    }
+"""
+    |> asLibrary
+    |> typeCheckWithStrictNullness
+    |> shouldSucceed
\ No newline at end of file
diff --git a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.debug.bsl b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.debug.bsl
index eeea1540744..7d20a88524a 100644
--- a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.debug.bsl
+++ b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.debug.bsl
@@ -1732,7 +1732,10 @@ Microsoft.FSharp.Core.Operators+Unchecked: Boolean Equals[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Compare[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Hash[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T DefaultOf[T]()
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNull[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Boolean IsNull[T](T)
 Microsoft.FSharp.Core.Operators: Boolean Not(Boolean)
 Microsoft.FSharp.Core.Operators: Boolean op_Equality[T](T, T)
@@ -1768,6 +1771,8 @@ Microsoft.FSharp.Core.Operators: Int64 ToInt64[T](T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.IntPtr], T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr[T](T)
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Collections.FSharpList`1[T] op_Append[T](Microsoft.FSharp.Collections.FSharpList`1[T], Microsoft.FSharp.Collections.FSharpList`1[T])
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeLeft[T2,T3,T1](Microsoft.FSharp.Core.FSharpFunc`2[T2,T3], Microsoft.FSharp.Core.FSharpFunc`2[T1,T2])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeRight[T1,T2,T3](Microsoft.FSharp.Core.FSharpFunc`2[T1,T2], Microsoft.FSharp.Core.FSharpFunc`2[T2,T3])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpOption`1[System.String] FailurePattern(System.Exception)
@@ -1797,6 +1802,8 @@ Microsoft.FSharp.Core.Operators: System.Exception Failure(System.String)
 Microsoft.FSharp.Core.Operators: System.IO.TextReader ConsoleIn[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleError[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleOut[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
 Microsoft.FSharp.Core.Operators: System.Object Box[T](T)
 Microsoft.FSharp.Core.Operators: System.RuntimeMethodHandle MethodHandleOf[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult])
 Microsoft.FSharp.Core.Operators: System.String NameOf[T](T)
@@ -1820,6 +1827,8 @@ Microsoft.FSharp.Core.Operators: T Cos[T](T)
 Microsoft.FSharp.Core.Operators: T Cosh$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Cosh[T](T)
 Microsoft.FSharp.Core.Operators: T DefaultArg[T](Microsoft.FSharp.Core.FSharpOption`1[T], T)
+Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
 Microsoft.FSharp.Core.Operators: T DefaultValueArg[T](Microsoft.FSharp.Core.FSharpValueOption`1[T], T)
 Microsoft.FSharp.Core.Operators: T Exit[T](Int32)
 Microsoft.FSharp.Core.Operators: T Exp$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
@@ -1837,6 +1846,11 @@ Microsoft.FSharp.Core.Operators: T Log10[T](T)
 Microsoft.FSharp.Core.Operators: T Log[T](T)
 Microsoft.FSharp.Core.Operators: T Max[T](T, T)
 Microsoft.FSharp.Core.Operators: T Min[T](T, T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNull[T](T)
+Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
 Microsoft.FSharp.Core.Operators: T NullArg[T](System.String)
 Microsoft.FSharp.Core.Operators: T PowInteger$W[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, Int32)
 Microsoft.FSharp.Core.Operators: T PowInteger[T](T, Int32)
@@ -1856,6 +1870,7 @@ Microsoft.FSharp.Core.Operators: T Tanh[T](T)
 Microsoft.FSharp.Core.Operators: T Truncate$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Truncate[T](T)
 Microsoft.FSharp.Core.Operators: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd[T](T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseOr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
@@ -1913,19 +1928,6 @@ Microsoft.FSharp.Core.Operators: Void Decrement(Microsoft.FSharp.Core.FSharpRef`
 Microsoft.FSharp.Core.Operators: Void Ignore[T](T)
 Microsoft.FSharp.Core.Operators: Void Increment(Microsoft.FSharp.Core.FSharpRef`1[System.Int32])
 Microsoft.FSharp.Core.Operators: Void op_ColonEquals[T](Microsoft.FSharp.Core.FSharpRef`1[T], T)
-Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
-Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNull[T](T)
-Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
-Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: FSharpFunc`3 Adapt(Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]])
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult] Invoke(T1)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: TResult Invoke(T1, T2)
diff --git a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.release.bsl b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.release.bsl
index 5b8c8858e96..e923211a3a2 100644
--- a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.release.bsl
+++ b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard20.release.bsl
@@ -1732,7 +1732,10 @@ Microsoft.FSharp.Core.Operators+Unchecked: Boolean Equals[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Compare[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Hash[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T DefaultOf[T]()
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNull[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Boolean IsNull[T](T)
 Microsoft.FSharp.Core.Operators: Boolean Not(Boolean)
 Microsoft.FSharp.Core.Operators: Boolean op_Equality[T](T, T)
@@ -1768,6 +1771,8 @@ Microsoft.FSharp.Core.Operators: Int64 ToInt64[T](T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.IntPtr], T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr[T](T)
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Collections.FSharpList`1[T] op_Append[T](Microsoft.FSharp.Collections.FSharpList`1[T], Microsoft.FSharp.Collections.FSharpList`1[T])
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeLeft[T2,T3,T1](Microsoft.FSharp.Core.FSharpFunc`2[T2,T3], Microsoft.FSharp.Core.FSharpFunc`2[T1,T2])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeRight[T1,T2,T3](Microsoft.FSharp.Core.FSharpFunc`2[T1,T2], Microsoft.FSharp.Core.FSharpFunc`2[T2,T3])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpOption`1[System.String] FailurePattern(System.Exception)
@@ -1797,6 +1802,8 @@ Microsoft.FSharp.Core.Operators: System.Exception Failure(System.String)
 Microsoft.FSharp.Core.Operators: System.IO.TextReader ConsoleIn[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleError[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleOut[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
 Microsoft.FSharp.Core.Operators: System.Object Box[T](T)
 Microsoft.FSharp.Core.Operators: System.String NameOf[T](T)
 Microsoft.FSharp.Core.Operators: System.String ToString[T](T)
@@ -1819,6 +1826,8 @@ Microsoft.FSharp.Core.Operators: T Cos[T](T)
 Microsoft.FSharp.Core.Operators: T Cosh$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Cosh[T](T)
 Microsoft.FSharp.Core.Operators: T DefaultArg[T](Microsoft.FSharp.Core.FSharpOption`1[T], T)
+Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
 Microsoft.FSharp.Core.Operators: T DefaultValueArg[T](Microsoft.FSharp.Core.FSharpValueOption`1[T], T)
 Microsoft.FSharp.Core.Operators: T Exit[T](Int32)
 Microsoft.FSharp.Core.Operators: T Exp$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
@@ -1836,6 +1845,11 @@ Microsoft.FSharp.Core.Operators: T Log10[T](T)
 Microsoft.FSharp.Core.Operators: T Log[T](T)
 Microsoft.FSharp.Core.Operators: T Max[T](T, T)
 Microsoft.FSharp.Core.Operators: T Min[T](T, T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNull[T](T)
+Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
 Microsoft.FSharp.Core.Operators: T NullArg[T](System.String)
 Microsoft.FSharp.Core.Operators: T PowInteger$W[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, Int32)
 Microsoft.FSharp.Core.Operators: T PowInteger[T](T, Int32)
@@ -1855,6 +1869,7 @@ Microsoft.FSharp.Core.Operators: T Tanh[T](T)
 Microsoft.FSharp.Core.Operators: T Truncate$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Truncate[T](T)
 Microsoft.FSharp.Core.Operators: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd[T](T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseOr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
@@ -1912,19 +1927,6 @@ Microsoft.FSharp.Core.Operators: Void Decrement(Microsoft.FSharp.Core.FSharpRef`
 Microsoft.FSharp.Core.Operators: Void Ignore[T](T)
 Microsoft.FSharp.Core.Operators: Void Increment(Microsoft.FSharp.Core.FSharpRef`1[System.Int32])
 Microsoft.FSharp.Core.Operators: Void op_ColonEquals[T](Microsoft.FSharp.Core.FSharpRef`1[T], T)
-Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
-Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNull[T](T)
-Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
-Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: FSharpFunc`3 Adapt(Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]])
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult] Invoke(T1)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: TResult Invoke(T1, T2)
@@ -2555,4 +2557,4 @@ Microsoft.FSharp.Reflection.UnionCaseInfo: System.String Name
 Microsoft.FSharp.Reflection.UnionCaseInfo: System.String ToString()
 Microsoft.FSharp.Reflection.UnionCaseInfo: System.String get_Name()
 Microsoft.FSharp.Reflection.UnionCaseInfo: System.Type DeclaringType
-Microsoft.FSharp.Reflection.UnionCaseInfo: System.Type get_DeclaringType()
+Microsoft.FSharp.Reflection.UnionCaseInfo: System.Type get_DeclaringType()
\ No newline at end of file
diff --git a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.debug.bsl b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.debug.bsl
index 5a5008e7218..7abc18b3057 100644
--- a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.debug.bsl
+++ b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.debug.bsl
@@ -1733,7 +1733,10 @@ Microsoft.FSharp.Core.Operators+Unchecked: Boolean Equals[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Compare[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Hash[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T DefaultOf[T]()
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNull[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Boolean IsNull[T](T)
 Microsoft.FSharp.Core.Operators: Boolean Not(Boolean)
 Microsoft.FSharp.Core.Operators: Boolean op_Equality[T](T, T)
@@ -1769,6 +1772,8 @@ Microsoft.FSharp.Core.Operators: Int64 ToInt64[T](T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.IntPtr], T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr[T](T)
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Collections.FSharpList`1[T] op_Append[T](Microsoft.FSharp.Collections.FSharpList`1[T], Microsoft.FSharp.Collections.FSharpList`1[T])
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeLeft[T2,T3,T1](Microsoft.FSharp.Core.FSharpFunc`2[T2,T3], Microsoft.FSharp.Core.FSharpFunc`2[T1,T2])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeRight[T1,T2,T3](Microsoft.FSharp.Core.FSharpFunc`2[T1,T2], Microsoft.FSharp.Core.FSharpFunc`2[T2,T3])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpOption`1[System.String] FailurePattern(System.Exception)
@@ -1798,6 +1803,8 @@ Microsoft.FSharp.Core.Operators: System.Exception Failure(System.String)
 Microsoft.FSharp.Core.Operators: System.IO.TextReader ConsoleIn[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleError[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleOut[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
 Microsoft.FSharp.Core.Operators: System.Object Box[T](T)
 Microsoft.FSharp.Core.Operators: System.RuntimeMethodHandle MethodHandleOf[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult])
 Microsoft.FSharp.Core.Operators: System.String NameOf[T](T)
@@ -1821,6 +1828,8 @@ Microsoft.FSharp.Core.Operators: T Cos[T](T)
 Microsoft.FSharp.Core.Operators: T Cosh$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Cosh[T](T)
 Microsoft.FSharp.Core.Operators: T DefaultArg[T](Microsoft.FSharp.Core.FSharpOption`1[T], T)
+Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
 Microsoft.FSharp.Core.Operators: T DefaultValueArg[T](Microsoft.FSharp.Core.FSharpValueOption`1[T], T)
 Microsoft.FSharp.Core.Operators: T Exit[T](Int32)
 Microsoft.FSharp.Core.Operators: T Exp$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
@@ -1838,6 +1847,11 @@ Microsoft.FSharp.Core.Operators: T Log10[T](T)
 Microsoft.FSharp.Core.Operators: T Log[T](T)
 Microsoft.FSharp.Core.Operators: T Max[T](T, T)
 Microsoft.FSharp.Core.Operators: T Min[T](T, T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNull[T](T)
+Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
 Microsoft.FSharp.Core.Operators: T NullArg[T](System.String)
 Microsoft.FSharp.Core.Operators: T PowInteger$W[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, Int32)
 Microsoft.FSharp.Core.Operators: T PowInteger[T](T, Int32)
@@ -1857,6 +1871,7 @@ Microsoft.FSharp.Core.Operators: T Tanh[T](T)
 Microsoft.FSharp.Core.Operators: T Truncate$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Truncate[T](T)
 Microsoft.FSharp.Core.Operators: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd[T](T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseOr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
@@ -1914,19 +1929,6 @@ Microsoft.FSharp.Core.Operators: Void Decrement(Microsoft.FSharp.Core.FSharpRef`
 Microsoft.FSharp.Core.Operators: Void Ignore[T](T)
 Microsoft.FSharp.Core.Operators: Void Increment(Microsoft.FSharp.Core.FSharpRef`1[System.Int32])
 Microsoft.FSharp.Core.Operators: Void op_ColonEquals[T](Microsoft.FSharp.Core.FSharpRef`1[T], T)
-Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
-Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNull[T](T)
-Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
-Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: FSharpFunc`3 Adapt(Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]])
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult] Invoke(T1)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: TResult Invoke(T1, T2)
diff --git a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.release.bsl b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.release.bsl
index 12f8380fbfb..a633fb0dc1b 100644
--- a/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.release.bsl
+++ b/tests/FSharp.Core.UnitTests/FSharp.Core.SurfaceArea.netstandard21.release.bsl
@@ -1733,7 +1733,10 @@ Microsoft.FSharp.Core.Operators+Unchecked: Boolean Equals[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Compare[T](T, T)
 Microsoft.FSharp.Core.Operators+Unchecked: Int32 Hash[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T DefaultOf[T]()
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators+Unchecked: T NonNull[T](T)
 Microsoft.FSharp.Core.Operators+Unchecked: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Boolean IsNull[T](T)
 Microsoft.FSharp.Core.Operators: Boolean Not(Boolean)
 Microsoft.FSharp.Core.Operators: Boolean op_Equality[T](T, T)
@@ -1769,6 +1772,8 @@ Microsoft.FSharp.Core.Operators: Int64 ToInt64[T](T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.IntPtr], T)
 Microsoft.FSharp.Core.Operators: IntPtr ToIntPtr[T](T)
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Collections.FSharpList`1[T] op_Append[T](Microsoft.FSharp.Collections.FSharpList`1[T], Microsoft.FSharp.Collections.FSharpList`1[T])
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
+Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeLeft[T2,T3,T1](Microsoft.FSharp.Core.FSharpFunc`2[T2,T3], Microsoft.FSharp.Core.FSharpFunc`2[T1,T2])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpFunc`2[T1,T3] op_ComposeRight[T1,T2,T3](Microsoft.FSharp.Core.FSharpFunc`2[T1,T2], Microsoft.FSharp.Core.FSharpFunc`2[T2,T3])
 Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpOption`1[System.String] FailurePattern(System.Exception)
@@ -1798,6 +1803,8 @@ Microsoft.FSharp.Core.Operators: System.Exception Failure(System.String)
 Microsoft.FSharp.Core.Operators: System.IO.TextReader ConsoleIn[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleError[T]()
 Microsoft.FSharp.Core.Operators: System.IO.TextWriter ConsoleOut[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
+Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
 Microsoft.FSharp.Core.Operators: System.Object Box[T](T)
 Microsoft.FSharp.Core.Operators: System.String NameOf[T](T)
 Microsoft.FSharp.Core.Operators: System.String ToString[T](T)
@@ -1820,6 +1827,8 @@ Microsoft.FSharp.Core.Operators: T Cos[T](T)
 Microsoft.FSharp.Core.Operators: T Cosh$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Cosh[T](T)
 Microsoft.FSharp.Core.Operators: T DefaultArg[T](Microsoft.FSharp.Core.FSharpOption`1[T], T)
+Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
 Microsoft.FSharp.Core.Operators: T DefaultValueArg[T](Microsoft.FSharp.Core.FSharpValueOption`1[T], T)
 Microsoft.FSharp.Core.Operators: T Exit[T](Int32)
 Microsoft.FSharp.Core.Operators: T Exp$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
@@ -1837,6 +1846,11 @@ Microsoft.FSharp.Core.Operators: T Log10[T](T)
 Microsoft.FSharp.Core.Operators: T Log[T](T)
 Microsoft.FSharp.Core.Operators: T Max[T](T, T)
 Microsoft.FSharp.Core.Operators: T Min[T](T, T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
+Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
+Microsoft.FSharp.Core.Operators: T NonNull[T](T)
+Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
 Microsoft.FSharp.Core.Operators: T NullArg[T](System.String)
 Microsoft.FSharp.Core.Operators: T PowInteger$W[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, Int32)
 Microsoft.FSharp.Core.Operators: T PowInteger[T](T, Int32)
@@ -1856,6 +1870,7 @@ Microsoft.FSharp.Core.Operators: T Tanh[T](T)
 Microsoft.FSharp.Core.Operators: T Truncate$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,T], T)
 Microsoft.FSharp.Core.Operators: T Truncate[T](T)
 Microsoft.FSharp.Core.Operators: T Unbox[T](System.Object)
+Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseAnd[T](T, T)
 Microsoft.FSharp.Core.Operators: T op_BitwiseOr$W[T](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[T,T]], T, T)
@@ -1913,19 +1928,6 @@ Microsoft.FSharp.Core.Operators: Void Decrement(Microsoft.FSharp.Core.FSharpRef`
 Microsoft.FSharp.Core.Operators: Void Ignore[T](T)
 Microsoft.FSharp.Core.Operators: Void Increment(Microsoft.FSharp.Core.FSharpRef`1[System.Int32])
 Microsoft.FSharp.Core.Operators: Void op_ColonEquals[T](Microsoft.FSharp.Core.FSharpRef`1[T], T)
-Microsoft.FSharp.Core.Operators: Boolean IsNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullMatchPattern[T](T)
-Microsoft.FSharp.Core.Operators: Microsoft.FSharp.Core.FSharpChoice`2[Microsoft.FSharp.Core.Unit,T] NullValueMatchPattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] NullV[T]()
-Microsoft.FSharp.Core.Operators: System.Nullable`1[T] WithNullV[T](T)
-Microsoft.FSharp.Core.Operators: T DefaultIfNullV[T](T, System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T DefaultIfNull[T](T, T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickPattern[T](T)
-Microsoft.FSharp.Core.Operators: T NonNullQuickValuePattern[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNullV[T](System.Nullable`1[T])
-Microsoft.FSharp.Core.Operators: T NonNull[T](T)
-Microsoft.FSharp.Core.Operators: T NullArgCheck[T](System.String, T)
-Microsoft.FSharp.Core.Operators: T WithNull[T](T)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: FSharpFunc`3 Adapt(Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]])
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult] Invoke(T1)
 Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`3[T1,T2,TResult]: TResult Invoke(T1, T2)

From a82e880d692692718f503a594fc4209b1f9b41b4 Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Tue, 6 Feb 2024 16:33:58 +0100
Subject: [PATCH 4/4] Lets not touch (+)

---
 src/FSharp.Core/prim-types.fs                   |  3 ---
 .../Language/NullableLibraryConstructsTests.fs  | 17 +++++++++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/FSharp.Core/prim-types.fs b/src/FSharp.Core/prim-types.fs
index 3ec0b8d19d7..b4e3271b60d 100644
--- a/src/FSharp.Core/prim-types.fs
+++ b/src/FSharp.Core/prim-types.fs
@@ -4434,9 +4434,6 @@ namespace Microsoft.FSharp.Core
              when ^T : sbyte       and ^U : sbyte      = (# "conv.i1" (# "add" x y : int32 #) : sbyte #)
              when ^T : byte        and ^U : byte       = (# "conv.u1" (# "add" x y : uint32 #) : byte #)
              when ^T : string      and ^U : string     = (# "" (String.Concat((# "" x : string #),(# "" y : string #))) : ^T #)
-#if !BUILDING_WITH_LKG && !NO_NULLCHECKING_LIB_SUPPORT
-             when ^T : (string|null) and ^U : (string|null) = (# "" (String.Concat((# "" x : string #),(# "" y : string #))) : string #)
-#endif
              when ^T : decimal     and ^U : decimal    = (# "" (Decimal.op_Addition((# "" x : decimal #),(# "" y : decimal #))) : ^V #)
              // According to the somewhat subtle rules of static optimizations,
              // this condition is used whenever ^T is resolved to a nominal type or witnesses are available
diff --git a/tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs b/tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs
index c68412e7859..790c4cfd395 100644
--- a/tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs
+++ b/tests/FSharp.Compiler.ComponentTests/Language/NullableLibraryConstructsTests.fs
@@ -36,6 +36,23 @@ let readAllLines (reader:System.IO.StreamReader) : seq<string> =
             match reader.ReadLine() with
             | Unchecked.NonNullQuick line -> yield line
     }
+"""
+    |> asLibrary
+    |> typeCheckWithStrictNullness
+    |> shouldSucceed
+
+[<Fact>]
+let ``Can concat two maybe null strings`` () =
+    FSharp """module MyLibrary
+
+let addStrings (x:string | null) (y:string) : string  =
+
+    let s2 = x + x
+    let s3 = y + y
+    let s4 = y + x
+    let s4string : string = s4
+
+    s4
 """
     |> asLibrary
     |> typeCheckWithStrictNullness