diff --git a/src/arrange_ir.ml b/src/arrange_ir.ml
index 36b574c3b7e..58b8760f23d 100644
--- a/src/arrange_ir.ml
+++ b/src/arrange_ir.ml
@@ -71,6 +71,7 @@ and dec d = match d.it with
     "TypD" $$ [con c; kind k]
 
 and typ_bind (tb : typ_bind) =
-  tb.it.Type.var $$ [typ tb.it.Type.bound]
+  Con.to_string tb.it.con $$ [typ tb.it.bound]
+
 
 and prog prog = "BlockE"  $$ List.map dec prog.it
diff --git a/src/async.ml b/src/async.ml
index 5938bbfd8b9..e91e6907cb4 100644
--- a/src/async.ml
+++ b/src/async.ml
@@ -375,8 +375,11 @@ and t_pat' pat =
   | AltP (pat1, pat2) ->
     AltP (t_pat pat1, t_pat pat2)
 
+and t_typ_bind' {con; bound} =
+  {con; bound = t_typ bound}
+
 and t_typ_bind typ_bind =
-  { typ_bind with it = t_bind typ_bind.it }
+  { typ_bind with it = t_typ_bind' typ_bind.it }
 
 and t_typ_binds typbinds = List.map t_typ_bind typbinds
 
diff --git a/src/check_ir.ml b/src/check_ir.ml
index d4a3f2472b3..95be4d11026 100644
--- a/src/check_ir.ml
+++ b/src/check_ir.ml
@@ -693,13 +693,16 @@ and cons_of_typ_binds typ_binds =
   List.map con_of_typ_bind typ_binds
 
 and check_open_typ_binds env typ_binds =
-  let cs = cons_of_typ_binds typ_binds in
-  let ks = List.map (fun tp -> T.Abs([],tp.it.T.bound)) typ_binds in
+  let cs = List.map (fun tp -> tp.it.con) typ_binds in
+  let ks = List.map (fun tp -> T.Abs([],tp.it.bound)) typ_binds in
   let ce = List.fold_right2 Con.Env.add cs ks Con.Env.empty in
-  let binds = T.close_binds cs (List.map (fun tb -> tb.it) typ_binds) in
+  let binds = close_typ_binds cs (List.map (fun tb -> tb.it) typ_binds) in
   let _,_ = check_typ_binds env binds in
   cs,ce
 
+and close_typ_binds cs tbs =
+  List.map (fun {con; bound} -> {Type.var = Con.name con; bound = Type.close cs bound}) tbs
+
 and check_dec env dec  =
   (* helpers *)
   let check p = check env dec.at p in
@@ -777,7 +780,7 @@ and gather_dec env scope dec : scope =
     { scope with val_env = ve}
   | FuncD (call_conv, id, typ_binds, pat, typ, exp) ->
     let func_sort = call_conv.Value.sort in
-    let cs = cons_of_typ_binds typ_binds in
+    let cs = List.map (fun tb -> tb.it.con) typ_binds in
     let t1 = pat.note in
     let t2 = typ in
     let ts1 = match call_conv.Value.n_args with
@@ -792,7 +795,7 @@ and gather_dec env scope dec : scope =
       | T.Sharable, (T.Async _) -> T.Promises  (* TBR: do we want this for T.Local too? *)
       | _ -> T.Returns
     in
-    let ts = List.map (fun typbind -> typbind.it.T.bound) typ_binds in
+    let ts = List.map (fun typbind -> typbind.it.bound) typ_binds in
     let tbs = List.map2 (fun c t -> {T.var = Con.name c; bound = T.close cs t}) cs ts in
     let t = T.Func (func_sort, c, tbs, List.map (T.close cs) ts1, List.map (T.close cs) ts2) in
     let ve' =  T.Env.add id.it t scope.val_env in
diff --git a/src/compile.ml b/src/compile.ml
index 7c77c1c4a15..94601a684f0 100644
--- a/src/compile.ml
+++ b/src/compile.ml
@@ -239,8 +239,8 @@ module E = struct
        This shoulds be extracte into Type.add_open_typ_binds
        and maybe we need a type open_typ_bind that can be used inside the IR.
     *)
-    let cs = Check_ir.cons_of_typ_binds typ_binds in
-    let ks = List.map (fun tp -> Type.Abs([],tp.it.Type.bound)) typ_binds in
+    let cs = List.map (fun tp -> tp.it.con) typ_binds in
+    let ks = List.map (fun tp -> Type.Abs([],tp.it.bound)) typ_binds in
     let ce = List.fold_right2 Con.Env.add cs ks Con.Env.empty in
     { env with con_env = Con.Env.adjoin env.con_env ce }
 
diff --git a/src/desugar.ml b/src/desugar.ml
index 393c5994ae2..becb43e73a9 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -128,9 +128,14 @@ and exp_field' (f : S.exp_field') =
 and typ_binds tbs = List.map typ_bind tbs
 
 and typ_bind tb =
-  phrase' typ_bind' tb
-
-and typ_bind' at n { S.var; S.bound } = { Type.var = var.it; Type.bound = bound.note }
+  let c = match tb.note with
+    | Some c -> c
+    | _ -> assert false
+  in
+  { it = { Ir.con = c; Ir.bound = tb.it.S.bound.note}
+  ; at = tb.at
+  ; note = ()
+  }
 
 and decs ds =
   match ds with
@@ -163,8 +168,8 @@ and dec' at n d = match d with
     let inst = List.map
                  (fun tb ->
                    match tb.note with
-                   | Type.Pre -> assert false
-                   | t -> t)
+                   | None -> assert false
+                   | Some c -> T.Con (c, []))
                  tbs in
     let obj_typ =
       match n.S.note_typ with
diff --git a/src/ir.ml b/src/ir.ml
index 69b1162163c..55b1aca6e63 100644
--- a/src/ir.ml
+++ b/src/ir.ml
@@ -3,7 +3,8 @@ type type_note = Syntax.typ_note = {note_typ : Type.typ; note_eff : Type.eff}
 
 type 'a phrase = ('a, Syntax.typ_note) Source.annotated_phrase
 
-type typ_bind = (Type.bind, Type.typ) Source.annotated_phrase
+and typ_bind' = {con : Con.t; bound : Type.typ}
+type typ_bind = typ_bind' Source.phrase
 
 type pat = (pat', Type.typ) Source.annotated_phrase
 and pat' =
diff --git a/src/parser.mly b/src/parser.mly
index 294e1cd3cd9..3d205e2c8c3 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -256,9 +256,9 @@ typ_field :
 
 typ_bind :
   | x=id SUB t=typ
-    { {var = x; bound = t} @! at $sloc }
+    { {var = x; bound = t} @= at $sloc }
   | x=id
-    { {var = x; bound = PrimT "Any" @! at $sloc} @! at $sloc }
+    { {var = x; bound = PrimT "Any" @! at $sloc} @= at $sloc }
 
 
 
diff --git a/src/syntax.ml b/src/syntax.ml
index eab511f8aad..01fa40b3ad1 100644
--- a/src/syntax.ml
+++ b/src/syntax.ml
@@ -42,7 +42,7 @@ and typ' =
 and typ_field = typ_field' Source.phrase
 and typ_field' = {id : id; typ : typ; mut : mut}
 
-and typ_bind = (typ_bind', Type.typ) Source.annotated_phrase
+and typ_bind = (typ_bind', Con.t option) Source.annotated_phrase
 and typ_bind' = {var : id; bound : typ}
 
 
diff --git a/src/tailcall.ml b/src/tailcall.ml
index 35f4df59122..00adecd6305 100644
--- a/src/tailcall.ml
+++ b/src/tailcall.ml
@@ -64,10 +64,10 @@ let bind env i (info:func_info option) : env =
 
 let are_generic_insts tbs insts =
   List.for_all2 (fun tb inst ->
-      match tb.note, inst with
-      | Con(c1,[]), Con(c2,[]) -> c1 = c2 (* conservative, but safe *)
-      | Con(c1,[]), _ -> false
-      | _,_ -> assert false) tbs insts
+      match inst with
+      | Con(c2,[]) -> tb.it.con = c2 (* conservative, but safe *)
+      |  _ -> false
+      ) tbs insts
 
 let rec tailexp env e =
   {e with it = exp' env e}
@@ -210,7 +210,7 @@ and dec' env d =
       in
       let env3 = pat env2 p  in (* shadow id if necessary *)
       let exp0' = tailexp env3 exp0 in
-      let cs = List.map (fun tb -> tb.note) tbs in
+      let cs = List.map (fun tb -> Con (tb.it.con, [])) tbs in
       if !tail_called then
         let ids = match typ d with
           | Func( _, _, _, dom, _) -> List.map (fun t -> fresh_id (open_ cs t)) dom
diff --git a/src/typing.ml b/src/typing.ml
index ad59595bef7..e5113c3ed5d 100644
--- a/src/typing.ml
+++ b/src/typing.ml
@@ -214,7 +214,7 @@ and check_typ_field env s typ_field : T.field =
 and check_typ_binds env typ_binds : T.con list * T.typ list * typ_env * con_env =
   let xs = List.map (fun typ_bind -> typ_bind.it.var.it) typ_binds in
   let cs = List.map (fun x -> Con.fresh x) xs in
-  List.iter2 (fun typ_bind c -> typ_bind.note <- T.Con (c, [])) typ_binds cs;
+  List.iter2 (fun typ_bind c -> typ_bind.note <- Some c) typ_binds cs;
   let te = List.fold_left2 (fun te typ_bind c ->
       let id = typ_bind.it.var in
       if T.Env.mem id.it te then