From c4df147c3d0acb7dcf50d6d054037057d06305c9 Mon Sep 17 00:00:00 2001
From: Don Syme <dsyme@users.noreply.github.com>
Date: Thu, 6 Apr 2017 16:11:23 +0100
Subject: [PATCH] fix 2661 (#2807)

* fix 2661

* add test
---
 src/fsharp/TastOps.fs               | 19 +++++++++++++++++--
 tests/fsharp/optimize/inline/lib.fs | 27 +++++++++++++++++++++++++++
 tests/fsharp/tests.fs               |  2 ++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/src/fsharp/TastOps.fs b/src/fsharp/TastOps.fs
index 52179e4b7..9860e00ec 100644
--- a/src/fsharp/TastOps.fs
+++ b/src/fsharp/TastOps.fs
@@ -6444,6 +6444,20 @@ let MultiLambdaToTupledLambda g vs body =
         tupledv, untupler body 
       
 
+let (|RefTuple|_|) expr = 
+    match expr with
+    | Expr.Op (TOp.Tuple (TupInfo.Const false),_,args,_) -> Some args
+    | _ -> None
+
+let MultiLambdaToTupledLambdaIfNeeded g (vs,arg) body = 
+    match vs,arg with 
+    | [],_ -> failwith "MultiLambdaToTupledLambda: expected some argments"
+    | [v],_ -> [(v,arg)],body 
+    | vs,RefTuple args when args.Length = vs.Length -> List.zip vs args,body
+    | vs,_  -> 
+        let tupledv, untupler =  untupledToRefTupled g vs
+        [(tupledv, arg)], untupler body 
+
 //--------------------------------------------------------------------------
 // Beta reduction via let-bindings. Reduce immediate apps. of lambdas to let bindings. 
 // Includes binding the immediate application of generic
@@ -6495,8 +6509,9 @@ let rec MakeApplicationAndBetaReduceAux g (f, fty, tyargsl : TType list list, ar
           match tryStripLambdaN argsl.Length f with 
           | Some (argvsl, body) -> 
                assert (argvsl.Length = argsl.Length)
-               let argvs,body = List.mapFoldBack (MultiLambdaToTupledLambda g) argvsl body
-               mkLetsBind m (mkCompGenBinds argvs argsl) body
+               let pairs,body = List.mapFoldBack (MultiLambdaToTupledLambdaIfNeeded g) (List.zip argvsl argsl) body
+               let argvs2, args2 = List.unzip (List.concat pairs)
+               mkLetsBind m (mkCompGenBinds argvs2 args2) body
           | _ -> 
               mkExprApplAux g f fty argsl m 
 
diff --git a/tests/fsharp/optimize/inline/lib.fs b/tests/fsharp/optimize/inline/lib.fs
index 5050560b0..d04958a78 100644
--- a/tests/fsharp/optimize/inline/lib.fs
+++ b/tests/fsharp/optimize/inline/lib.fs
@@ -2,6 +2,8 @@ namespace ThisNamespaceHasToBeTheSame
 
 #nowarn "9"
 
+open System
+
 open System.Runtime.InteropServices
 
 [<Struct>]
@@ -131,3 +133,28 @@ do()
 
 [<System.Runtime.CompilerServices.InternalsVisibleToAttribute("lib3--optimize")>]
 do()
+
+[<NoEquality; NoComparison>]
+[<Struct>]
+type StructInt32 =
+    val mutable Value: int32
+    new(value) = { Value = value }
+    static member Write(value, x: StructInt32 byref) =
+        x.Value <- value;
+    static member inline InlineWrite(value, x: StructInt32 byref) =
+        x.Value <- value;
+
+module PeverifyTest = 
+    // The test here is simply to peverify the code
+    let ``StaticWriteResultANewValue`` () =
+        let mutable v = StructInt32(3);
+        StructInt32.Write(2, &v);
+        let result = v.Value
+        (2, result)
+
+    // The test here is simply to peverify the code
+    let ``StaticInlineWriteResultANewValue`` () =
+        let mutable v = StructInt32(3)
+        StructInt32.InlineWrite(2, &v)
+        let result = v.Value
+        (2, result)
diff --git a/tests/fsharp/tests.fs b/tests/fsharp/tests.fs
index b6e402701..bed6d7f34 100644
--- a/tests/fsharp/tests.fs
+++ b/tests/fsharp/tests.fs
@@ -1586,6 +1586,8 @@ module OptimizationTests =
 
         fsc cfg "%s -g --optimize- --target:library -o:lib.dll" cfg.fsc_flags ["lib.fs"; "lib2.fs"]
 
+        peverify cfg "lib.dll " 
+
         fsc cfg "%s -g --optimize- --target:library -o:lib3.dll -r:lib.dll " cfg.fsc_flags ["lib3.fs"]
 
         fsc cfg "%s -g --optimize- -o:test.exe -r:lib.dll -r:lib3.dll" cfg.fsc_flags ["test.fs "]
-- 
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