Merge pull request #5406 from KevinRansom/cherrypick_3

Cherrypick 3 --- better fix for #5369 (#5398) 

src/fsharp/TastPickle.fs

@@ -121,7 +121,6 @@ type WriterState =
     onlerefs: Table<int * int[]> 
     osimpletys: Table<int>
     oglobals : TcGlobals
-    mutable isStructThisArgPos : bool
     ofile : string
     /// Indicates if we are using in-memory format, where we store XML docs as well
     oInMem : bool
@@ -506,9 +505,13 @@ let p_maybe_lazy p (x: MaybeLazy<_>) st =
     p_lazy_impl p x.Value st
 
 let p_hole () = 
-    let h = ref (None : 'T pickler option)
+    let h = ref (None : ('T -> WriterState -> unit) option)
     (fun f -> h := Some f),(fun x st -> match !h with Some f -> f x st | None -> pfailwith st "p_hole: unfilled hole")
 
+let p_hole2 () = 
+    let h = ref (None : ('Arg -> 'T -> WriterState -> unit) option)
+    (fun f -> h := Some f),(fun arg x st -> match !h with Some f -> f arg x st | None -> pfailwith st "p_hole2: unfilled hole")
+
 let u_array_core f n st =
     let res = Array.zeroCreate n
     for i = 0 to n-1 do
@@ -710,8 +713,7 @@ let pickleObjWithDanglingCcus inMem file g scope p x =
         osimpletys=Table<_>.Create "osimpletys"  
         oglobals=g
         ofile=file
-        oInMem=inMem
-        isStructThisArgPos = false}
+        oInMem=inMem }
     p x st1
     let sizes = 
       st1.otycons.Size,
@@ -733,8 +735,7 @@ let pickleObjWithDanglingCcus inMem file g scope p x =
        osimpletys=Table<_>.Create "osimpletys (fake)"
        oglobals=g
        ofile=file
-       oInMem=inMem
-       isStructThisArgPos = false }
+       oInMem=inMem }
     p_tup7
       (p_array p_encoded_ccuref) 
       (p_tup3 p_int p_int p_int) 
@@ -1266,7 +1267,9 @@ let u_rfref st = let a,b = u_tup2 u_tcref u_string st in RFRef(a,b)
 let u_tpref st = u_local_item_ref st.itypars st
 
 // forward reference
-let fill_p_ty,p_ty = p_hole()
+let fill_p_ty2,p_ty2 = p_hole2()
+
+let p_ty = p_ty2 false
 let p_tys = (p_list p_ty)
 
 let fill_p_attribs,p_attribs = p_hole()
@@ -1291,9 +1294,7 @@ let p_nonlocal_val_ref (nlv:NonLocalValOrMemberRef) st =
         match key.TypeForLinkage with 
         | None -> false
         | Some ty -> checkForInRefStructThisArg st ty
-    st.isStructThisArgPos <- isStructThisArgPos
-    p_option p_ty key.TypeForLinkage st
-    st.isStructThisArgPos <- false
+    p_option (p_ty2 isStructThisArgPos) key.TypeForLinkage st
 
 let rec p_vref ctxt x st = 
     match x with 
@@ -1553,9 +1554,17 @@ let u_tyar_spec st =
 
 let u_tyar_specs = (u_list u_tyar_spec)
 
-let _ = fill_p_ty (fun ty st ->
+let _ = fill_p_ty2 (fun isStructThisArgPos ty st ->
     let ty = stripTyparEqns ty
-    let ty = if isInByrefTy st.oglobals ty && st.isStructThisArgPos then destByrefTy st.oglobals ty else ty
+
+    // See comment on 'checkForInRefStructThisArg'
+    let ty = 
+        if isInByrefTy st.oglobals ty && isStructThisArgPos then 
+            // Convert the inref to a byref 
+            mkByrefTy st.oglobals (destByrefTy st.oglobals ty) 
+        else
+            ty
+
     match ty with 
     | TType_tuple (tupInfo,l) -> 
           if evalTupInfoIsStruct tupInfo then 
@@ -1566,11 +1575,15 @@ let _ = fill_p_ty (fun ty st ->
     | TType_app (tc,tinst)              -> p_byte 2 st; p_tup2 (p_tcref "typ") p_tys (tc,tinst) st
     | TType_fun (d,r)                   -> 
         p_byte 3 st
-        p_ty d st
-        st.isStructThisArgPos <- false
+        // Note, the "this" argument may be found in the domain position of a function type, so propagate the isStructThisArgPos value
+        p_ty2 isStructThisArgPos d st
         p_ty r st
     | TType_var r                       -> p_byte 4 st; p_tpref r st
-    | TType_forall (tps,r)              -> p_byte 5 st; p_tup2 p_tyar_specs p_ty (tps,r) st
+    | TType_forall (tps,r)              -> 
+        p_byte 5 st
+        p_tyar_specs tps st
+        // Note, the "this" argument may be found in the body of a generic forall type, so propagate the isStructThisArgPos value
+        p_ty2 isStructThisArgPos r st
     | TType_measure unt                 -> p_byte 6 st; p_measure_expr unt st
     | TType_ucase (uc,tinst)            -> p_byte 7 st; p_tup2 p_ucref p_tys (uc,tinst) st)
 
@@ -1838,9 +1851,7 @@ and p_ValData x st =
     p_ranges (x.ValReprInfo |> Option.map (fun _ -> x.val_range, x.DefinitionRange)) st
     
     let isStructThisArgPos = x.IsMember && checkForInRefStructThisArg st x.Type
-    st.isStructThisArgPos <- isStructThisArgPos
-    p_ty x.val_type st
-    st.isStructThisArgPos <- false
+    p_ty2 isStructThisArgPos x.val_type st
 
     p_int64 x.val_flags.PickledBits st
     p_option p_member_info x.MemberInfo st