Optimize PreComputeTupleConstructor

src/fsharp/FSharp.Core/reflect.fs

@@ -158,6 +158,35 @@ module internal Impl =
                 param)
         expr.Compile ()
 
+    let compileTupleConstructor tupleEncField getTupleConstructorMethod typ =
+        let rec constituentTuple (typ: Type) elements startIndex =
+            Expression.New (
+                getTupleConstructorMethod typ,
+                [
+                    let genericArgs = typ.GetGenericArguments ()
+
+                    for paramIndex in 0 .. genericArgs.Length - 1 do
+                        let genericArg = genericArgs.[paramIndex]
+
+                        if paramIndex = tupleEncField then
+                            constituentTuple genericArg elements (startIndex + paramIndex) :> Expression
+                        else
+                            Expression.Convert (Expression.ArrayAccess (elements, Expression.Constant (startIndex + paramIndex)), genericArg)
+                ])
+
+        let elements = Expression.Parameter (typeof<obj[]>, "elements")
+
+        let expr =
+            Expression.Lambda<Func<obj[], obj>> (
+                Expression.Convert (
+                    constituentTuple typ elements 0,
+                    typeof<obj>
+                ),
+                elements
+            )
+
+        expr.Compile ()
+
     //-----------------------------------------------------------------
     // ATTRIBUTE DECOMPILATION
 
@@ -988,7 +1017,7 @@ type FSharpValue =
 
     static member PreComputeTupleConstructor(tupleType: Type) =
         checkTupleType("tupleType", tupleType)
-        getTupleConstructor tupleType
+        (compileTupleConstructor tupleEncField getTupleConstructorMethod tupleType).Invoke
 
     static member PreComputeTupleConstructorInfo(tupleType: Type) =
         checkTupleType("tupleType", tupleType)

tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Reflection/FSharpReflection.fs

@@ -118,10 +118,12 @@ type FSharpValueTests() =
     let tuple1 = ( 1, "tuple1")
     let tuple2 = ( 2, "tuple2", (fun x -> x + 1))
     let tuple3 = ( 1, ( 2, "tuple"))
+    let longTuple = (("yup", 1s), 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, Some 12, 13, "nope", struct (15, 16), 17, 18, ValueSome 19)
 
     let structTuple1 = struct ( 1, "tuple1")
     let structTuple2 = struct ( 2, "tuple2", (fun x -> x + 1))
     let structTuple3 = struct ( 1, struct ( 2, "tuple"))
+    let longStructTuple = struct (("yup", 1s), 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, Some 12, 13, "nope", struct (15, 16), 17, 18, ValueSome 19)
 
     let func1  param  = param + 1
     let func2  param  = param + ""
@@ -550,6 +552,9 @@ type FSharpValueTests() =
         // Tuple
         let tupleCtor = FSharpValue.PreComputeTupleConstructor(tuple1.GetType())    
         Assert.AreEqual( tupleCtor([| box 1; box "tuple1" |]) , box(tuple1))
+
+        let tupleCtor = FSharpValue.PreComputeTupleConstructor(longTuple.GetType())    
+        Assert.AreEqual( tupleCtor([| box ("yup", 1s); box 2; box 3; box 4; box 5; box 6; box 7; box 8; box 9; box 10; box 11; box (Some 12); box 13; box "nope"; box (struct (15, 16)); box 17; box 18; box (ValueSome 19) |]) , box(longTuple))
 
         // Tuple with function member
         let tuplewithFuncCtor = FSharpValue.PreComputeTupleConstructor(tuple2.GetType())  
@@ -573,6 +578,9 @@ type FSharpValueTests() =
         let tupleCtor = FSharpValue.PreComputeTupleConstructor(structTuple1.GetType())    
         Assert.AreEqual( tupleCtor([| box 1; box "tuple1" |]) , box(structTuple1))
 
+        let tupleCtor = FSharpValue.PreComputeTupleConstructor(longStructTuple.GetType())    
+        Assert.AreEqual( tupleCtor([| box ("yup", 1s); box 2; box 3; box 4; box 5; box 6; box 7; box 8; box 9; box 10; box 11; box (Some 12); box 13; box "nope"; box (struct (15, 16)); box 17; box 18; box (ValueSome 19) |]) , box(longStructTuple))
+
         // Tuple with function member
         let tuplewithFuncCtor = FSharpValue.PreComputeTupleConstructor(structTuple2.GetType())  
         let resultTuplewithFunc = tuplewithFuncCtor([| box 2; box "tuple2"; box (fun x -> x + 1) |])

tests/fsharp/Compiler/Libraries/Core/Reflection/PreComputedTupleConstructorTests.fs

@@ -25,4 +25,4 @@ module ``PreComputedTupleConstructor Tests`` =
         let testDelegate = TestDelegate (fun () -> 
             Reflection.FSharpValue.PreComputeTupleConstructor(typeof<int * string>) [| box "text"; box 12; |] |> ignore)
 
-        Assert.Throws<System.ArgumentException> testDelegate |> ignore
+        Assert.Throws<System.InvalidCastException> testDelegate |> ignore