diff --git a/src/fsharp/FSharp.Core.Unittests/FSharp.Core/Microsoft.FSharp.Core/OptionModule.fs b/src/fsharp/FSharp.Core.Unittests/FSharp.Core/Microsoft.FSharp.Core/OptionModule.fs
index b2010567f13..595eb7457cc 100644
--- a/src/fsharp/FSharp.Core.Unittests/FSharp.Core/Microsoft.FSharp.Core/OptionModule.fs
+++ b/src/fsharp/FSharp.Core.Unittests/FSharp.Core/Microsoft.FSharp.Core/OptionModule.fs
@@ -18,6 +18,15 @@ Make sure each method works on:
 [<TestFixture>]
 type OptionModule() =
 
+    let assertWasNotCalledThunk () = raise (exn "Thunk should not have been called.")
+
+    [<Test>]
+    member this.Flatten () =
+        Assert.AreEqual( Option.flatten None, None)
+        Assert.AreEqual( Option.flatten (Some None), None)
+        Assert.AreEqual( Option.flatten (Some <| Some 1), Some 1)
+        Assert.AreEqual( Option.flatten (Some <| Some ""), Some "") 
+
     [<Test>]
     member this.FilterSomeIntegerWhenPredicateReturnsTrue () =
         let test x =
@@ -98,7 +107,17 @@ type OptionModule() =
             let expected = None
             Assert.AreEqual(expected, actual)
         [""; "     "; "Baz Quux"; "Corge grault"] |> List.iter test
-        
+
+    [<Test>]
+    member this.Contains() =
+        Assert.IsFalse( Option.contains 1 None)
+        Assert.IsTrue( Option.contains 1 (Some 1))
+
+        Assert.IsFalse( Option.contains "" None)
+        Assert.IsTrue( Option.contains "" (Some ""))
+
+        Assert.IsFalse( Option.contains None None)
+        Assert.IsTrue( Option.contains None (Some None))
     [<Test>]
     member this.OfToNullable() =
         Assert.IsTrue( Option.ofNullable (System.Nullable<int>()) = None)
@@ -121,4 +140,79 @@ type OptionModule() =
         Assert.IsTrue( Option.ofObj (null : string array) = None)
         Assert.IsTrue( Option.ofObj<string> null = None)
         Assert.IsTrue( Option.ofObj<string[]> null = None)
-        Assert.IsTrue( Option.ofObj<int[]> null = None)
\ No newline at end of file
+        Assert.IsTrue( Option.ofObj<int[]> null = None)
+
+    [<Test>]
+    member this.DefaultValue() =
+        Assert.AreEqual( Option.defaultValue 3 None, 3)
+        Assert.AreEqual( Option.defaultValue 3 (Some 42), 42)
+        Assert.AreEqual( Option.defaultValue "" None, "")
+        Assert.AreEqual( Option.defaultValue "" (Some "x"), "x")
+
+    [<Test>]
+    member this.DefaultWith() =
+        Assert.AreEqual( Option.defaultWith (fun () -> 3) None, 3)
+        Assert.AreEqual( Option.defaultWith (fun () -> "") None, "")
+
+        Assert.AreEqual( Option.defaultWith assertWasNotCalledThunk (Some 42), 42)
+        Assert.AreEqual( Option.defaultWith assertWasNotCalledThunk (Some ""), "")
+
+    [<Test>]
+    member this.OrElse() =
+        Assert.AreEqual( Option.orElse None None, None)
+        Assert.AreEqual( Option.orElse (Some 3) None, Some 3)
+        Assert.AreEqual( Option.orElse None (Some 42), Some 42)
+        Assert.AreEqual( Option.orElse (Some 3) (Some 42), Some 42)
+
+        Assert.AreEqual( Option.orElse (Some "") None, Some "")
+        Assert.AreEqual( Option.orElse None (Some "x"), Some "x")
+        Assert.AreEqual( Option.orElse (Some "") (Some "x"), Some "x")
+
+    [<Test>]
+    member this.OrElseWith() =
+        Assert.AreEqual( Option.orElseWith (fun () -> None) None, None)
+        Assert.AreEqual( Option.orElseWith (fun () -> Some 3) None, Some 3)
+        Assert.AreEqual( Option.orElseWith (fun () -> Some "") None, Some "")
+
+        Assert.AreEqual( Option.orElseWith assertWasNotCalledThunk (Some 42), Some 42)
+        Assert.AreEqual( Option.orElseWith assertWasNotCalledThunk (Some ""), Some "")
+
+    [<Test>]
+    member this.Map2() =
+        Assert.AreEqual( Option.map2 (-) None None, None)
+        Assert.AreEqual( Option.map2 (-) (Some 1) None, None)
+        Assert.AreEqual( Option.map2 (-) None (Some 2), None)
+        Assert.AreEqual( Option.map2 (-) (Some 1) (Some 2), Some -1)
+
+        Assert.AreEqual( Option.map2 (+) None None, None)
+        Assert.AreEqual( Option.map2 (+) (Some "x") None, None)
+        Assert.AreEqual( Option.map2 (+) None (Some "y"), None)
+        Assert.AreEqual( Option.map2 (+) (Some "x") (Some "y"), Some "xy")
+
+    [<Test>]
+    member this.Map3() =
+        let add3 x y z = string x + string y + string z
+        Assert.AreEqual( Option.map3 add3 None None None, None)
+        Assert.AreEqual( Option.map3 add3 (Some 1) None None, None)
+        Assert.AreEqual( Option.map3 add3 None (Some 2) None, None)
+        Assert.AreEqual( Option.map3 add3 (Some 1) (Some 2) None, None)
+        Assert.AreEqual( Option.map3 add3 None None (Some 3), None)
+        Assert.AreEqual( Option.map3 add3 (Some 1) None (Some 3), None)
+        Assert.AreEqual( Option.map3 add3 None (Some 2) (Some 3), None)
+        Assert.AreEqual( Option.map3 add3 (Some 1) (Some 2) (Some 3), Some "123")
+
+        let concat3 x y z = x + y + z
+        Assert.AreEqual( Option.map3 concat3 None None None, None)
+        Assert.AreEqual( Option.map3 concat3 (Some "x") None None, None)
+        Assert.AreEqual( Option.map3 concat3 None (Some "y") None, None)
+        Assert.AreEqual( Option.map3 concat3 (Some "x") (Some "y") None, None)
+        Assert.AreEqual( Option.map3 concat3 None None (Some "z"), None)
+        Assert.AreEqual( Option.map3 concat3 (Some "x") None (Some "z"), None)
+        Assert.AreEqual( Option.map3 concat3 None (Some "y") (Some "z"), None)
+        Assert.AreEqual( Option.map3 concat3 (Some "x") (Some "y") (Some "z"), Some "xyz")
+
+    [<Test>]
+    member this.MapBindEquivalenceProperties () =
+        let fn x = x + 3
+        Assert.AreEqual(Option.map fn None, Option.bind (fn >> Some) None)
+        Assert.AreEqual(Option.map fn (Some 5), Option.bind (fn >> Some) (Some 5))
\ No newline at end of file
diff --git a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.coreclr.fs b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.coreclr.fs
index 10c4389cb95..f2f634cab1f 100644
--- a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.coreclr.fs
+++ b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.coreclr.fs
@@ -2713,6 +2713,7 @@ Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures
 Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`6[T1,T2,T3,T4,T5,TResult]
 Microsoft.FSharp.Core.OptimizedClosures: System.String ToString()
 Microsoft.FSharp.Core.OptimizedClosures: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: Boolean Contains[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean Equals(System.Object)
 Microsoft.FSharp.Core.OptionModule: Boolean Exists[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean ForAll[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
@@ -2722,13 +2723,20 @@ Microsoft.FSharp.Core.OptionModule: Int32 Count[T](Microsoft.FSharp.Core.FSharpO
 Microsoft.FSharp.Core.OptionModule: Int32 GetHashCode()
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Collections.FSharpList`1[T] ToList[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Bind[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpOption`1[TResult]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map2[T1,T2,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map3[T1,T2,T3,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,Microsoft.FSharp.Core.FSharpFunc`2[T3,TResult]]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2], Microsoft.FSharp.Core.FSharpOption`1[T3])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Filter[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Flatten[T](Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpOption`1[T]])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfNullable[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfObj[T](T)
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElseWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,Microsoft.FSharp.Core.FSharpOption`1[T]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElse[T](Microsoft.FSharp.Core.FSharpOption`1[T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.Nullable`1[T] ToNullable[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.String ToString()
 Microsoft.FSharp.Core.OptionModule: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: T DefaultValue[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: T DefaultWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T GetValue[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T ToObj[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: TState FoldBack[T,TState](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[TState,TState]], Microsoft.FSharp.Core.FSharpOption`1[T], TState)
diff --git a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.net40.fs b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.net40.fs
index c452c3f31c4..99d38a69f95 100644
--- a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.net40.fs
+++ b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.net40.fs
@@ -2747,6 +2747,7 @@ Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures
 Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`6[T1,T2,T3,T4,T5,TResult]
 Microsoft.FSharp.Core.OptimizedClosures: System.String ToString()
 Microsoft.FSharp.Core.OptimizedClosures: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: Boolean Contains[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean Equals(System.Object)
 Microsoft.FSharp.Core.OptionModule: Boolean Exists[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean ForAll[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
@@ -2756,13 +2757,20 @@ Microsoft.FSharp.Core.OptionModule: Int32 Count[T](Microsoft.FSharp.Core.FSharpO
 Microsoft.FSharp.Core.OptionModule: Int32 GetHashCode()
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Collections.FSharpList`1[T] ToList[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Bind[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpOption`1[TResult]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map2[T1,T2,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map3[T1,T2,T3,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,Microsoft.FSharp.Core.FSharpFunc`2[T3,TResult]]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2], Microsoft.FSharp.Core.FSharpOption`1[T3])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Filter[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Flatten[T](Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpOption`1[T]])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfNullable[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfObj[T](T)
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElseWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,Microsoft.FSharp.Core.FSharpOption`1[T]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElse[T](Microsoft.FSharp.Core.FSharpOption`1[T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.Nullable`1[T] ToNullable[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.String ToString()
 Microsoft.FSharp.Core.OptionModule: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: T DefaultValue[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: T DefaultWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T GetValue[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T ToObj[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: TState FoldBack[T,TState](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[TState,TState]], Microsoft.FSharp.Core.FSharpOption`1[T], TState)
diff --git a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable259.fs b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable259.fs
index 8e5337ef4a8..d799117f863 100644
--- a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable259.fs
+++ b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable259.fs
@@ -2718,6 +2718,7 @@ Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures
 Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`6[T1,T2,T3,T4,T5,TResult]
 Microsoft.FSharp.Core.OptimizedClosures: System.String ToString()
 Microsoft.FSharp.Core.OptimizedClosures: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: Boolean Contains[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean Equals(System.Object)
 Microsoft.FSharp.Core.OptionModule: Boolean Exists[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean ForAll[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
@@ -2727,13 +2728,20 @@ Microsoft.FSharp.Core.OptionModule: Int32 Count[T](Microsoft.FSharp.Core.FSharpO
 Microsoft.FSharp.Core.OptionModule: Int32 GetHashCode()
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Collections.FSharpList`1[T] ToList[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Bind[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpOption`1[TResult]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map2[T1,T2,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map3[T1,T2,T3,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,Microsoft.FSharp.Core.FSharpFunc`2[T3,TResult]]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2], Microsoft.FSharp.Core.FSharpOption`1[T3])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Filter[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Flatten[T](Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpOption`1[T]])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfNullable[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfObj[T](T)
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElseWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,Microsoft.FSharp.Core.FSharpOption`1[T]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElse[T](Microsoft.FSharp.Core.FSharpOption`1[T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.Nullable`1[T] ToNullable[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.String ToString()
 Microsoft.FSharp.Core.OptionModule: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: T DefaultValue[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: T DefaultWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T GetValue[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T ToObj[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: TState FoldBack[T,TState](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[TState,TState]], Microsoft.FSharp.Core.FSharpOption`1[T], TState)
diff --git a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable47.fs b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable47.fs
index 531eebf0e8f..9c0f389633d 100644
--- a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable47.fs
+++ b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable47.fs
@@ -2719,6 +2719,7 @@ Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures
 Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`6[T1,T2,T3,T4,T5,TResult]
 Microsoft.FSharp.Core.OptimizedClosures: System.String ToString()
 Microsoft.FSharp.Core.OptimizedClosures: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: Boolean Contains[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean Equals(System.Object)
 Microsoft.FSharp.Core.OptionModule: Boolean Exists[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean ForAll[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
@@ -2728,13 +2729,20 @@ Microsoft.FSharp.Core.OptionModule: Int32 Count[T](Microsoft.FSharp.Core.FSharpO
 Microsoft.FSharp.Core.OptionModule: Int32 GetHashCode()
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Collections.FSharpList`1[T] ToList[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Bind[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpOption`1[TResult]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map2[T1,T2,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map3[T1,T2,T3,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,Microsoft.FSharp.Core.FSharpFunc`2[T3,TResult]]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2], Microsoft.FSharp.Core.FSharpOption`1[T3])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Filter[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Flatten[T](Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpOption`1[T]])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfNullable[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfObj[T](T)
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElseWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,Microsoft.FSharp.Core.FSharpOption`1[T]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElse[T](Microsoft.FSharp.Core.FSharpOption`1[T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.Nullable`1[T] ToNullable[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.String ToString()
 Microsoft.FSharp.Core.OptionModule: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: T DefaultValue[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: T DefaultWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T GetValue[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T ToObj[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: TState FoldBack[T,TState](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[TState,TState]], Microsoft.FSharp.Core.FSharpOption`1[T], TState)
diff --git a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable7.fs b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable7.fs
index 7d320ad8483..b9de41ca1eb 100644
--- a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable7.fs
+++ b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable7.fs
@@ -2731,6 +2731,7 @@ Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures
 Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`6[T1,T2,T3,T4,T5,TResult]
 Microsoft.FSharp.Core.OptimizedClosures: System.String ToString()
 Microsoft.FSharp.Core.OptimizedClosures: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: Boolean Contains[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean Equals(System.Object)
 Microsoft.FSharp.Core.OptionModule: Boolean Exists[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean ForAll[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
@@ -2740,13 +2741,20 @@ Microsoft.FSharp.Core.OptionModule: Int32 Count[T](Microsoft.FSharp.Core.FSharpO
 Microsoft.FSharp.Core.OptionModule: Int32 GetHashCode()
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Collections.FSharpList`1[T] ToList[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Bind[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpOption`1[TResult]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map2[T1,T2,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map3[T1,T2,T3,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,Microsoft.FSharp.Core.FSharpFunc`2[T3,TResult]]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2], Microsoft.FSharp.Core.FSharpOption`1[T3])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Filter[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Flatten[T](Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpOption`1[T]])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfNullable[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfObj[T](T)
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElseWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,Microsoft.FSharp.Core.FSharpOption`1[T]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElse[T](Microsoft.FSharp.Core.FSharpOption`1[T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.Nullable`1[T] ToNullable[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.String ToString()
 Microsoft.FSharp.Core.OptionModule: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: T DefaultValue[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: T DefaultWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T GetValue[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T ToObj[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: TState FoldBack[T,TState](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[TState,TState]], Microsoft.FSharp.Core.FSharpOption`1[T], TState)
diff --git a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable78.fs b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable78.fs
index f731fcdbcc0..aedaca4bff3 100644
--- a/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable78.fs
+++ b/src/fsharp/FSharp.Core.Unittests/SurfaceArea.portable78.fs
@@ -2718,6 +2718,7 @@ Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures
 Microsoft.FSharp.Core.OptimizedClosures: Microsoft.FSharp.Core.OptimizedClosures+FSharpFunc`6[T1,T2,T3,T4,T5,TResult]
 Microsoft.FSharp.Core.OptimizedClosures: System.String ToString()
 Microsoft.FSharp.Core.OptimizedClosures: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: Boolean Contains[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean Equals(System.Object)
 Microsoft.FSharp.Core.OptionModule: Boolean Exists[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Boolean ForAll[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
@@ -2727,13 +2728,20 @@ Microsoft.FSharp.Core.OptionModule: Int32 Count[T](Microsoft.FSharp.Core.FSharpO
 Microsoft.FSharp.Core.OptionModule: Int32 GetHashCode()
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Collections.FSharpList`1[T] ToList[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Bind[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpOption`1[TResult]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map2[T1,T2,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,TResult]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map3[T1,T2,T3,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T1,Microsoft.FSharp.Core.FSharpFunc`2[T2,Microsoft.FSharp.Core.FSharpFunc`2[T3,TResult]]], Microsoft.FSharp.Core.FSharpOption`1[T1], Microsoft.FSharp.Core.FSharpOption`1[T2], Microsoft.FSharp.Core.FSharpOption`1[T3])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[TResult] Map[T,TResult](Microsoft.FSharp.Core.FSharpFunc`2[T,TResult], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Filter[T](Microsoft.FSharp.Core.FSharpFunc`2[T,System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] Flatten[T](Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpOption`1[T]])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfNullable[T](System.Nullable`1[T])
 Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OfObj[T](T)
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElseWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,Microsoft.FSharp.Core.FSharpOption`1[T]], Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: Microsoft.FSharp.Core.FSharpOption`1[T] OrElse[T](Microsoft.FSharp.Core.FSharpOption`1[T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.Nullable`1[T] ToNullable[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: System.String ToString()
 Microsoft.FSharp.Core.OptionModule: System.Type GetType()
+Microsoft.FSharp.Core.OptionModule: T DefaultValue[T](T, Microsoft.FSharp.Core.FSharpOption`1[T])
+Microsoft.FSharp.Core.OptionModule: T DefaultWith[T](Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Core.Unit,T], Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T GetValue[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: T ToObj[T](Microsoft.FSharp.Core.FSharpOption`1[T])
 Microsoft.FSharp.Core.OptionModule: TState FoldBack[T,TState](Microsoft.FSharp.Core.FSharpFunc`2[T,Microsoft.FSharp.Core.FSharpFunc`2[TState,TState]], Microsoft.FSharp.Core.FSharpOption`1[T], TState)
diff --git a/src/fsharp/FSharp.Core/option.fs b/src/fsharp/FSharp.Core/option.fs
index 3bca435ce6b..17a5c41591b 100644
--- a/src/fsharp/FSharp.Core/option.fs
+++ b/src/fsharp/FSharp.Core/option.fs
@@ -16,6 +16,18 @@ namespace Microsoft.FSharp.Core
         [<CompiledName("IsNone")>]
         let inline isNone option = match option with None -> true | Some _ -> false
 
+        [<CompiledName("DefaultValue")>]
+        let defaultValue def option = match option with None -> def | Some v -> v
+
+        [<CompiledName("DefaultWith")>]
+        let defaultWith defThunk option = match option with None -> defThunk () | Some v -> v
+
+        [<CompiledName("OrElse")>]
+        let orElse ifNone option = match option with None -> ifNone | Some _ -> option
+
+        [<CompiledName("OrElseWith")>]
+        let orElseWith ifNoneThunk option = match option with None -> ifNoneThunk () | Some _ -> option
+
         [<CompiledName("Count")>]
         let count option = match option with None -> 0 | Some _ -> 1
 
@@ -31,15 +43,33 @@ namespace Microsoft.FSharp.Core
         [<CompiledName("ForAll")>]
         let forall p inp = match inp with None -> true | Some x -> p x
 
+        [<CompiledName("Contains")>]
+        let inline contains x inp = match inp with None -> false | Some v -> v = x
+
         [<CompiledName("Iterate")>]
         let iter f inp = match inp with None -> () | Some x -> f x
 
         [<CompiledName("Map")>]
         let map f inp = match inp with None -> None | Some x -> Some (f x)
 
+        [<CompiledName("Map2")>]
+        let map2 f option1 option2 = 
+            match option1, option2 with
+            | Some x, Some y -> Some <| f x y
+            | _ -> None
+
+        [<CompiledName("Map3")>]
+        let map3 f option1 option2 option3 = 
+            match option1, option2, option3 with
+            | Some x, Some y, Some z -> Some <| f x y z
+            | _ -> None
+
         [<CompiledName("Bind")>]
         let bind f inp = match inp with None -> None | Some x -> f x
 
+        [<CompiledName("Flatten")>]
+        let flatten option = match option with None -> None | Some x -> x
+
         [<CompiledName("Filter")>]
         let filter f inp = match inp with None -> None | Some x -> if f x then Some x else None
 
diff --git a/src/fsharp/FSharp.Core/option.fsi b/src/fsharp/FSharp.Core/option.fsi
index 3225893e284..7296d739366 100644
--- a/src/fsharp/FSharp.Core/option.fsi
+++ b/src/fsharp/FSharp.Core/option.fsi
@@ -23,6 +23,37 @@ namespace Microsoft.FSharp.Core
         [<CompiledName("IsNone")>]
         val inline isNone: option:'T option -> bool
 
+        /// <summary>Gets the value of the option if the option is <c>Some</c>, otherwise returns the specified default value.</summary>
+        /// <param name="value">The specified default value.</param>
+        /// <param name="option">The input option.</param>
+        /// <returns>The option if the option is Some, else the default value.</returns>
+        /// <remarks>Identical to the built-in <see cref="defaultArg"/> operator, except with the arguments swapped.</remarks>
+        [<CompiledName("DefaultValue")>]
+        val defaultValue: value:'T -> option:'T option -> 'T
+
+        /// <summary>Gets the value of the option if the option is <c>Some</c>, otherwise evaluates <paramref name="defThunk"/> and returns the result.</summary>
+        /// <param name="defThunk">A thunk that provides a default value when evaluated.</param>
+        /// <param name="option">The input option.</param>
+        /// <returns>The option if the option is Some, else the result of evaluating <paramref name="defThunk"/>.</returns>
+        /// <remarks><paramref name="defThunk"/> is not evaluated unless <paramref name="option"/> is <c>None</c>.</remarks>
+        [<CompiledName("DefaultWith")>]
+        val defaultWith: defThunk:(unit -> 'T) -> option:'T option -> 'T
+
+        /// <summary>Returns <paramref name="option"/> if it is <c>Some</c>, otherwise returns <paramref name="ifNone"/>.</summary>
+        /// <param name="ifNone">The value to use if <paramref name="option"/> is <c>None</c>.</param>
+        /// <param name="option">The input option.</param>
+        /// <returns>The option if the option is Some, else the alternate option.</returns>
+        [<CompiledName("OrElse")>]
+        val orElse: ifNone:'T option -> option:'T option -> 'T option
+
+        /// <summary>Returns <paramref name="option"/> if it is <c>Some</c>, otherwise evaluates <paramref name="ifNoneThunk"/> and returns the result.</summary>
+        /// <param name="ifNoneThunk">A thunk that provides an alternate option when evaluated.</param>
+        /// <param name="option">The input option.</param>
+        /// <returns>The option if the option is Some, else the result of evaluating <paramref name="ifNoneThunk"/>.</returns>
+        /// <remarks><paramref name="ifNoneThunk"/> is not evaluated unless <paramref name="option"/> is <c>None</c>.</remarks>
+        [<CompiledName("OrElseWith")>]
+        val orElseWith: ifNoneThunk:(unit -> 'T option) -> option:'T option -> 'T option
+
         /// <summary>Gets the value associated with the option.</summary>
         /// <param name="option">The input option.</param>
         /// <returns>The value within the option.</returns>
@@ -70,6 +101,13 @@ namespace Microsoft.FSharp.Core
         [<CompiledName("ForAll")>]
         val forall: predicate:('T -> bool) -> option:'T option -> bool
 
+        /// <summary>Evaluates to true if <paramref name="option"/> is <c>Some</c> and its value is equal to <paramref name="value"/>.</summary>
+        /// <param name="value">The value to test for equality.</param>
+        /// <param name="option">The input option.</param>
+        /// <returns>True if the option is <c>Some</c> and contains a value equal to <paramref name="value"/>, otherwise false.</returns>
+        [<CompiledName("Contains")>]
+        val inline contains: value:'T -> option:'T option -> bool when 'T : equality
+
         /// <summary><c>iter f inp</c> executes <c>match inp with None -> () | Some x -> f x</c>.</summary>
         /// <param name="action">A function to apply to the option value.</param>
         /// <param name="option">The input option.</param>
@@ -85,6 +123,23 @@ namespace Microsoft.FSharp.Core
         [<CompiledName("Map")>]
         val map: mapping:('T -> 'U) -> option:'T option -> 'U option
 
+        /// <summary><c>map f option1 option2</c> evaluates to <c>match option1, option2 with Some x, Some y -> Some (f x y) | _ -> None</c>.</summary>
+        /// <param name="mapping">A function to apply to the option values.</param>
+        /// <param name="option1">The first option.</param>
+        /// <param name="option2">The second option.</param>
+        /// <returns>An option of the input values after applying the mapping function, or None if either input is None.</returns>
+        [<CompiledName("Map2")>]
+        val map2: mapping:('T1 -> 'T2 -> 'U) -> 'T1 option -> 'T2 option -> 'U option
+
+        /// <summary><c>map f option1 option2 option3</c> evaluates to <c>match option1, option2, option3 with Some x, Some y, Some z -> Some (f x y z) | _ -> None</c>.</summary>
+        /// <param name="mapping">A function to apply to the option values.</param>
+        /// <param name="option1">The first option.</param>
+        /// <param name="option2">The second option.</param>
+        /// <param name="option3">The third option.</param>
+        /// <returns>An option of the input values after applying the mapping function, or None if any input is None.</returns>
+        [<CompiledName("Map3")>]
+        val map3: mapping:('T1 -> 'T2 -> 'T3 -> 'U) -> 'T1 option -> 'T2 option -> 'T3 option -> 'U option
+
         /// <summary><c>bind f inp</c> evaluates to <c>match inp with None -> None | Some x -> f x</c></summary>
         /// <param name="binder">A function that takes the value of type T from an option and transforms it into
         /// an option containing a value of type U.</param>
@@ -93,6 +148,13 @@ namespace Microsoft.FSharp.Core
         [<CompiledName("Bind")>]
         val bind: binder:('T -> 'U option) -> option:'T option -> 'U option
 
+        /// <summary><c>flatten inp</c> evaluates to <c>match inp with None -> None | Some x -> x</c></summary>
+        /// <param name="option">The input option.</param>
+        /// <returns>An option of the output type of the binder.</returns>
+        /// <remarks><c>flatten</c> is equivalent to <c>bind id</c>.</remarks>
+        [<CompiledName("Flatten")>]
+        val flatten: option:'T option option -> 'T option
+
         /// <summary><c>filter f inp</c> evaluates to <c>match inp with None -> None | Some x -> if f x then Some x else None</c>.</summary>
         /// <param name="predicate">A function that evaluates whether the value contained in the option should remain, or be filtered out.</param>
         /// <param name="option">The input option.</param>
diff --git a/tests/fsharpqa/testenv/bin/System.ValueTuple.dll b/tests/fsharpqa/testenv/bin/System.ValueTuple.dll
new file mode 100644
index 00000000000..9b6bbf8db5f
Binary files /dev/null and b/tests/fsharpqa/testenv/bin/System.ValueTuple.dll differ