Remove nonlocal_ modality (#1452)

* remove `nonlocal_` modality

* bootstrap

* address review comments

ocaml/boot/menhir/parser.mli

@@ -41,7 +41,6 @@ type token =
   | OF
   | OBJECT
   | NONREC
-  | NONLOCAL
   | NEW
   | MUTABLE
   | MODULE

ocaml/parsing/asttypes.mli

@@ -46,7 +46,6 @@ type closed_flag = Closed | Open
 
 type global_flag =
   | Global
-  | Nonlocal
   | Nothing
 
 (* constant layouts are parsed as layout annotations, and also used

ocaml/parsing/builtin_attributes.ml

@@ -96,7 +96,6 @@ let builtin_attrs =
   ; "local_opt"; "ocaml.local_opt"
   ; "curry"; "ocaml.curry"; "extension.curry"
   ; "global"; "ocaml.global"; "extension.global"
-  ; "nonlocal"; "ocaml.nonlocal"; "extension.nonlocal"
   ; "local"; "ocaml.local"; "extension.local"
   ; "nontail"; "ocaml.nontail"; "extension.nontail"
   ; "tail"; "ocaml.tail"; "extension.tail"
@@ -634,9 +633,6 @@ let has_local attr =
 let has_global attrs =
   check_local ["extension.global"] ["ocaml.global"; "global"] attrs
 
-let has_nonlocal attrs =
-  check_local ["extension.nonlocal"] ["ocaml.nonlocal"; "nonlocal"] attrs
-
 let tailcall attr =
   let has_nontail = has_attribute ["ocaml.nontail"; "nontail"] attr in
   let tail_attrs = filter_attributes [["ocaml.tail";"tail"], true] attr in

ocaml/parsing/builtin_attributes.mli

@@ -168,7 +168,6 @@ val has_curry: Parsetree.attributes -> bool
    are present despite the extension being disabled *)
 val has_local: Parsetree.attributes -> (bool,unit) result
 val has_global: Parsetree.attributes -> (bool,unit) result
-val has_nonlocal: Parsetree.attributes -> (bool,unit) result
 val tailcall : Parsetree.attributes ->
     ([`Tail|`Nontail|`Tail_if_possible] option, [`Conflict]) result
 

ocaml/parsing/jane_syntax.mli

@@ -207,7 +207,7 @@ module Core_type : sig
 end
 
 (** Novel syntax in constructor arguments; this isn't a core AST type,
-    but captures where [global_] and [nonlocal_] live *)
+    but captures where [global_] lives *)
 module Constructor_argument : sig
   type t = |
 

ocaml/parsing/lexer.mll

@@ -72,7 +72,6 @@ let keyword_table =
     "module", MODULE;
     "mutable", MUTABLE;
     "new", NEW;
-    "nonlocal_", NONLOCAL;
     "nonrec", NONREC;
     "object", OBJECT;
     "of", OF;

ocaml/parsing/parser.mly

@@ -216,33 +216,20 @@ let global_loc loc = mkloc "extension.global" loc
 let global_attr loc =
   mk_attr ~loc:loc (global_loc loc) (PStr [])
 
-let nonlocal_loc loc = mkloc "extension.nonlocal" loc
-
-let nonlocal_attr loc =
-  mk_attr ~loc:Location.none (nonlocal_loc loc) (PStr [])
-
 let mkld_global ld loc =
   { ld with pld_attributes = global_attr loc :: ld.pld_attributes }
 
-let mkld_nonlocal ld loc =
-  { ld with pld_attributes = nonlocal_attr loc :: ld.pld_attributes }
-
 let mkld_global_maybe gbl ld loc =
   match gbl with
   | Global -> mkld_global ld loc
-  | Nonlocal -> mkld_nonlocal ld loc
   | Nothing -> ld
 
 let mkcty_global cty loc =
   { cty with ptyp_attributes = global_attr loc :: cty.ptyp_attributes }
 
-let mkcty_nonlocal cty loc =
-  { cty with ptyp_attributes = nonlocal_attr loc :: cty.ptyp_attributes }
-
 let mkcty_global_maybe gbl cty loc =
   match gbl with
   | Global -> mkcty_global cty loc
-  | Nonlocal -> mkcty_nonlocal cty loc
   | Nothing -> cty
 
 (* TODO define an abstraction boundary between locations-as-pairs
@@ -935,7 +922,6 @@ let mkpat_jane_syntax
 %token MODULE                 "module"
 %token MUTABLE                "mutable"
 %token NEW                    "new"
-%token NONLOCAL               "nonlocal_"
 %token NONREC                 "nonrec"
 %token OBJECT                 "object"
 %token OF                     "of"
@@ -4203,12 +4189,10 @@ mutable_or_global_flag:
     /* empty */                                 { Immutable, Nothing }
   | MUTABLE                                     { Mutable, Nothing }
   | GLOBAL                                      { Immutable, Global }
-  | NONLOCAL                                    { Immutable, Nonlocal }
 ;
 %inline global_flag:
           { Nothing }
   | GLOBAL { Global }
-  | NONLOCAL { Nonlocal }
 ;
 virtual_flag:
     /* empty */                                 { Concrete }
@@ -4289,7 +4273,6 @@ single_attr_id:
   | FUN { "fun" }
   | FUNCTION { "function" }
   | FUNCTOR { "functor" }
-  | NONLOCAL { "nonlocal_" }
   | IF { "if" }
   | IN { "in" }
   | INCLUDE { "include" }

ocaml/parsing/pprintast.ml

@@ -1673,14 +1673,13 @@ and record_declaration ctxt f lbls =
   in
   let field_flag f pld =
     pp f "%a" mutable_flag pld.pld_mutable;
-    if has_attr pld "extension.nonlocal" then pp f "nonlocal_ ";
     if has_attr pld "extension.global" then pp f "global_ "
   in
   let type_record_field f pld =
     let pld_attributes =
       List.filter (fun attr ->
         match attr.attr_name.txt with
-        | "extension.nonlocal" | "extension.global" -> false
+        | "extension.global" -> false
         | _ -> true) pld.pld_attributes
     in
     pp f "@[<2>%a%s:@;%a@;%a@]"

ocaml/testsuite/tests/typing-local/example_syntax.ml

@@ -7,7 +7,6 @@ let f () =
   local_ "asdfasdfasdfasdfasdfasdfasdf"
 type 'a r = {
   mutable a: 'a ;
-  nonlocal_ b: 'a ;
   global_ c: 'a }
 type ('a, 'b) cfn =
   a:local_ 'a -> ?b:local_ b -> local_ 'a -> (int -> local_ 'b)

ocaml/testsuite/tests/typing-local/exclave.ml

@@ -131,28 +131,17 @@ Line 3, characters 4-17:
 Error: Exclave expression should only be in tail position of the current region
 |}]
 
-type t = { nonlocal_ x : int option }
+type t = { x : int option }
 
 let foo (local_ x) =
-  let __ = { x } in
+  let _ = { x } in
   exclave_ x
 
 [%%expect{|
-type t = { nonlocal_ x : int option; }
+type t = { x : int option; }
 val foo : local_ int option -> local_ int option = <fun>
 |}]
 
-let foo (local_ x) =
-  let _ = { x } in
-  exclave_ { x }
-
-[%%expect{|
-Line 3, characters 13-14:
-3 |   exclave_ { x }
-                 ^
-Error: This local value escapes its region
-|}]
-
 (* semantics tests *)
 
 type data = {mutable a : string}